The sentence "It was not until he came back" is an incomplete thought. It sets up a situation where something happened after someone returned, but it doesn't tell us what happened afterward. To complete the thought, you would need to add a result or consequence. Here are some examples of how you could finish this sentence:

1. "It was not until he came back that we realized how much we missed him."
2. "It was not until he came back that the party started."
3. "It was not until he came back that the investigation could continue."
4. "It was not until he came back that she could finally tell him how she felt."

Each of these sentences uses "it was not until... that..." to indicate that a specific event or condition occurred only after the person returned. If you provide more context or specify the intended meaning, I can help you construct a more precise and fitting ending to your sentence.

It was not until he came back_____ I left the office.
A then
B which
C that
D when

C

解析

直到他回来，我才离开办公室。 [考点] 强调句 【精析】C 强调句型的基本结构为：It is/was +被强调部分+ that/who+其他。被强调的部分通常为主语、宾语和状语。如果被强调部分是人，连接词可以用who,也可以用that；如果被强调部分是物，连接词只能用that。本句强调时间