It was not until the end of prehistoric times that the first wheeled vehicles appearing.
Đáp án D: appearing -> appeared ( động từ chính của mệnh đề chia ở thì quá khứ đơn)
The Lake District,____________________ was made a national park in 1951, attracts a large number of tourists every year.
He_______________us but he was short of money at the time.
Supporters of free-market globalization point out that_____________________ .
Michael looked deeply hurt and surprised when_____________________ .
The packages___________________ so that it would be easier to carry them.
Education in many countries is compulsory________the age of 16.
She asked me______I was looking at.
There has been a great increase in retail sales,_____________________ ?
The pool should not be made so deep______small children can be safe there.
_______ has been a topic of continual geological research.