The tense used in the sentence "She will have already prepared food when I reach home" is Future Perfect.

This tense is formed by using "will have" followed by the past participle of the main verb. It is used to indicate an action that will be completed before a specific point in the future. In this case, "will have prepared" indicates that the preparation of the food will be completed before the speaker reaches home in the future.

Present Continuous: This tense is used to describe actions that are happening at the moment of speaking or actions that are happening around the time of speaking. The sentence "She is already preparing food when I reach home" would use the present continuous tense to indicate that the action of preparing food is ongoing at the time the speaker reaches home. However, this option doesn't match the structure of the given sentence.

Future Continuous: This tense is used to describe actions that will be ongoing at a specified time in the future. The sentence "She will be preparing food when I reach home" would use the future continuous tense to indicate that the action of preparing food will be ongoing at the time the speaker reaches home. However, this option doesn't match the structure of the given sentence.

Past Indefinite (Simple Past): This tense is used to describe actions that happened at a specific point in the past. The sentence "She prepared food when I reached home" would use the past indefinite tense to indicate that the action of preparing food occurred at the time the speaker reached home in the past. However, this option doesn't match the intended meaning of the given sentence.

Future Perfect: This tense is used to describe actions that will be completed before a specific point in the future. The sentence "She will have already prepared food when I reach home" uses the future perfect tense to indicate that the preparation of the food will be completed before the speaker reaches home in the future. This option matches the structure and intended meaning of the given sentence.

In summary, the correct tense for the given sentence is Future Perfect.

Hence option D is the correct answer .

Tense : - The tense of a verb in a sentence expresses time the event has occurred. There are three tenses of a verb: Present, Past and Future: time now, time then and time to come.

Future Perfect Tense:  Future Perfect Tense is used for actions that will be completed by a certain time in future.

Structure of Sentence : Subject + Will/Shall/Would + HAVE + V3 ( third form of main verb – past participle )  + Object

Example:

• I will have completed my graduation by then.

In the question : -

1. Lakshmi _____________  by then.

In this sentence , the correct form of tense that can be placed in the blank part is will have arrived as it is used to show an action that will be completed by a certain time in future.

2. The train ____________ by the time you reach the station.

In this sentence , the correct form of tense that can be placed in the blank part is will have left as it is used to show an action that will be completed by a certain time in future.

3. Diana _____________  home by Monday.

In this sentence , the correct form of tense that can be placed in the blank part is will have reached as it is used to show an action that will be completed by a certain time in future.

Thus , the Correct Option is C , which is Will have arrived , Will have left , Will have reached .

Tense : - The tense of a verb in a sentence expresses time the event has occurred. There are three tenses of a verb: Present, Past and Future: time now, time then and time to come.

Future Perfect Tense:  Future Perfect Tense is used for actions that will be completed by a certain time in future.

Structure of Sentence : Subject + Will/Shall/Would + HAVE + V3 ( third form of main verb – past participle )  + Object

Example:

• I will have completed my graduation by then.

In the question : -

1. I think all the plants ______________  before I return.

In this sentence , the correct form of tense that can be placed in the blank part is will have grown as it is used to show an action that will be completed by a certain time in future.

2. Sindhu _______________ anything by now. 

In this sentence , the correct form of tense that can be placed in the blank part is will not have forgotten as it is used to show an action that will be completed by a certain time in future.

3. He _____________ all the songs by heart before anyone else does. 

In this sentence , the correct form of tense that can be placed in the blank part is will have learnt as it is used to show an action that will be completed by a certain time in future.

Thus , the Correct Option is D , which is Will have grown , Will not have forgotten , Will have learnt .