The correct answer is C. failed/was enjoying.
The sentence is in the past tense, so we know that the action happened before now. The word “almost” tells us that the action almost happened, but it didn’t. The word “because” tells us that the action was caused by something else.
The only option that makes sense in the context of the sentence is C. failed/was enjoying. This option tells us that the action (failing) happened before now, and it was caused by something else (enjoying his social life too much).
The other options are not correct because they do not make sense in the context of the sentence. Option A, fails/has enjoyed, tells us that the action (failing) is happening now, but the sentence is in the past tense. Option B, was failing/has been enjoying, tells us that the action (failing) was happening before now, but it was not caused by something else. Option D, has been failing/enjoyed, tells us that the action (failing) has been happening for a long time, but the sentence does not tell us how long the action was happening. Option E, has failed/enjoys, tells us that the action (failing) happened in the past and it is still happening now, but the sentence does not tell us that the action is still happening now.