I wish he ............. with me that day. a) had come b) was c) had been d) would be

The correct answer is a) had come.

This sentence is in the third conditional, which is used to express a situation that didn't happen in the past. The structure of the third conditional is: if + past perfect (had + past participle), would have + past participle.

So, in the sentence "I wish he ............. with me that day", the correct form is "had come" because it follows the structure of the third conditional. The verb "come" is in the past participle form, which is necessary after "had" in this case.

The other options "was", "had been", and "would be" do not fit in this sentence because they do not follow the structure of the third conditional.