Tense : Tense is the time of a verb's action or its state of being, such as present (something happening now), past (something happened earlier), or future (something going to happen). These are called the verb's time frame. For example, examine I walk (present), I walked (past), and I will walk (future).

Future Perfect Continuous Tense:

Future Perfect Continuous Tense expresses an action that will have begun before a specific time and will be continuing till that time in future.

Example:

• She will have been reading for two hours.

In the question :

1. When I finish this course, I ____________ English for twenty years.In this sentence , the correct form of tense that can be placed in the blank part is will have been learning as it is used to show an action that will have begun before a specific time and will be continuing till that time in future.

2. Next year I _________________  here for four years. In this sentence , the correct form of tense that can be placed in the blank part is will have been working as it is used to show an action that will have begun before a specific time and will be continuing till that time in future.

Thus , the Correct Option is C , which is  Will have been learning , Will have been working .

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 Continuous Tense:

Future Perfect Continuous Tense expresses an action that will have begun before a specific time and will be continuing till that time in future.

Examples:

• She will have been reading for two hours.

In the question : -

1. Ram _____________  for an hour by the time I meet him.

In this sentence , the correct form of tense that can be placed in the blank part is will have been waiting as it is used to show an action that will have begun before a specific time and will be continuing till that time in future.

2. He ________________ long enough to qualify.

In this sentence , the correct form of tense that can be placed in the blank part is won't have been studying as it is used to show an action that will have begun before a specific time and will be continuing till that time in future. Won't is the contraction of will and not .

3. She _________________ swimming non-stop for over thirteen hours.

In this sentence , the correct form of tense that can be placed in the blank part is will have been swimming as it is used to show an action that will have begun before a specific time and will be continuing till that time in future.

Thus , the Correct Option is D , which is Will have been waiting , Won't have been studying , Will have been swimming .

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 Continuous Tense:

Future Perfect Continuous Tense expresses an action that will have begun before a specific time and will be continuing till that time in future.

Examples:

• She will have been reading for two hours.

In the question : -

1. I ________________ here for three hours by six o'clock. In this sentence , the correct form of tense that can be placed in the blank part is will have been waiting as it is used to show an action that will have begun before a specific time and will be continuing till that time in future.

2. By 2001 I _____________  in London for sixteen years. In this sentence , the correct form of tense that can be placed in the blank part is will have been living an action that will have begun before a specific time and will be continuing till that time in future.

Thus , the Correct Option is B , which is Will have been waiting , Will have been living .