FIND OUT THE MISTAKE IN THE FOLLOWING SENTENCE

câu 23: - BAI KIEM TRA TIENG NANG CAO LOP 10 SO 1
Lớp 10 BAI KIEM TRA TIENG NANG CAO LOP 10 SO 1

Câu 23:

Find out the mistake in the following sentence : At what age did Helen master Braille so well as the manual alphabet

A. did

B. age

C. so

D. At