Mr. Nixon refused to answer the questions on the that the matter was confidential.

Chọn đáp án: C. grounds
on the grounds that (idm) = because + clause: do bởi
Đáp án còn lại: A. reason (s) (n): lí do
B. excuse (s) (n): lời xin lỗi
D. foundation(s) (n): nền tảng
Tạm dịch: Ông Nixon đã từ chối trả lời các câu hỏi này bởi vì đây là vấn đề bảo mật.

Mr. Nixon refused to answer the questions on the ______ that the matter was confidential.