The sharp increase in the percentage of children living with single parents that began around 1960 has leveled off and was about the same in 2003 as it had been in 1990.

A

Giải thích : level off = khựng lại

1. remain stable = vẫn ổn định
2. increase slightly = tăng nhẹ
3. reduce quickly = giảm nhanh
4. fluctuate = dao động lên xuống , thay đổi thất thường

Vậy level off = remain stable . Đáp án A