The correct answer is: A. to have seen
The sentence “I am glad to have seen the movie” is in the present perfect tense. The present perfect tense is used to talk about things that have happened or been completed in the past, but have a connection to the present. In this case, the speaker is glad that they saw the movie because it was enjoyable or informative, and they are still thinking about it or benefiting from it in the present.
The other options are incorrect because they are not in the present perfect tense. Option B, “to see,” is in the infinitive form. The infinitive form is used to express purpose or intention. In this case, it would mean that the speaker intends to see the movie in the future. Option C, “had seen,” is in the past perfect tense. The past perfect tense is used to talk about things that happened or were completed before a specific time in the past. In this case, it would mean that the speaker saw the movie before some other event that happened in the past. Option D, “saw,” is in the simple past tense. The simple past tense is used to talk about things that happened or were completed at a specific time in the past. In this case, it would mean that the speaker saw the movie at some point in the past, but they are not necessarily thinking about it or benefiting from it in the present.