21. ____________ on the phone. It is his mother whom is It was his mot

21. ____________ on the phone.

• A. It is his mother whom is
• B. It was his mother whom is
• C. It was his mother who is
• D. It is his mother who is

Câu chẻ nhấn mạnh chủ ngữ là người, hai câu cùng thì HTĐ

It + is/was + Noun/pronoun (danh từ/đại từ - chỉ người) + that/who + V + O