reticent

尽管我们问了多次，他仍然对自己的过去保持沉默。

Despite our repeated questions, he remained ___reticent about his past.

这位首席执行官在投资者电话会议中对合并事宜守口如瓶。

The CEO remained ___reticent about the merger during the investor call.

同事们问起升职的事时，她一反常态地缄默不语。

When colleagues asked about the promotion, she was unusually ___reticent.