Last year he almost . . . . . . . . because he . . . . . . . . his social life a little too much.

In the given sentence "Last year he almost failed because he was enjoying his social life a little too much," the verbs "failed" and "was enjoying" are the correct choices to fill in the blanks.

"Last year he almost failed" - "failed" is the simple past tense of the verb "fail," indicating an action that happened and was completed in the past.
"because he was enjoying his social life a little too much" - "was enjoying" is the past continuous tense of the verb "enjoy," used to describe an ongoing action in the past. The continuous tense is appropriate here because it indicates that he was actively involved in enjoying his social life, which was an ongoing activity during that time.

The other options do not use the correct verb forms for the given sentence. Option A, "fails/has enjoyed," combines the simple present tense with the present perfect tense, which does not match the past tense context. Option B, "was failing/has been enjoying," combines the past continuous tense with the present perfect continuous tense, which is not suitable for this context. Option D, "has been failing/enjoyed," uses the present perfect continuous tense with the simple past tense, which does not fit the sentence structure. Option E, "has failed/enjoys," uses the present perfect tense with the simple present tense, which is also not appropriate for the past context.

Therefore, the correct answer is "C. failed/was enjoying."