Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainity or necessity.They indicate the attitude, intension and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

CAN AND COULD:

• Can is used to express physical or mental ability, capacity, capability. e.g.

          (a) I can solve this puzzle.

• Could is used in present context also, but with condition. e.g.

Could you get another job? ( if you lose this )

                The use of could in perfect tense shows such a past possibility that didn't take place or the action was actually not performed. e.g.

He could have sent a message ( but he didnt send).

                 The use of could in above constructions can also express irritation at or reproach for the non- performance of an action.

In the question : -

1. What _______ she say, I wonder?

In this sentence , can is the correct modal that can be placed in the blank part as it is used to show impatience anger of the speaker.

2. He _______ have caught the train, if he had hurried .

In this sentence ,  could is the correct modal that can be placed in the blank part as it is used to show  a past possibility that didn' t take place or the action was actually not performed and in past we use have with could .

Thus , the Correct Option is C , which is  Can , Could .

Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainty or necessity.They indicate the attitude, intention and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

CAN AND COULD:

• Can is used to express physical or mental ability, capacity, capability. e.g.

          (a) I can solve this puzzle.

• Could is used in present context also, but with condition. e.g.

Could you get another job? ( if you lose this )

                The use of could in perfect tense shows such a past possibility that didn't take place or the action was actually not performed. e.g.

He could have sent a message ( but he didnt send).

                 The use of could in above constructions can also express irritation at or reproach for the non- performance of an action.

In the question : -

1. _____ you lift this suitcase ?

In this sentence , can is the correct modal that can be placed in the blank part as it is used to show physical capability of someone .

2. _____ you operate the machine by yourself ?

In this sentence , could is the correct modal that can be placed in the blank part as it is used to show something which is in present context also but with condition  .

Thus , the Correct Option is C , which is  Can , Could .

Modals: They are verbs which are used before the main verb to express ability, possibility, obligation, permission, suggestion, request, certainty or necessity.They indicate the attitude, intention and the mood of the speaker.

• They cannot be used alone in a sentence.
• In case of Questions they are used alone.
• They are not affected by the change in person i.e. first, second or third form.
• Present Participle or Past Participle form of a verb is never used with a modal.

CAN AND COULD:

• Can is used to express physical or mental ability, capacity, capability. e.g.

          (a) I can solve this puzzle.

• Could is used in present context also, but with condition. e.g.

Could you get another job? ( if you lose this )

                The use of could in perfect tense shows such a past possibility that didn't take place or the action was actually not performed. e.g.

He could have sent a message ( but he didnt send).

                 The use of could in above constructions can also express irritation at or reproach for the non- performance of an action.

In the question : -

1. You can go there by road now.

In this sentence , can is the correct modal that can be placed in the blank part as it is used to shows the circumstantial possibility.

2. Could you operate the machine by yourself ?

In this sentence , could is the modal which is used to  present context also, but with condition.

Thus , the Correct Option is B , which is Can , Could .