问题
选择题
________ Pierre began to help his father with the farm work when he was
A．In 1980’s; his teens
B．At the 1980’s; the teens
C．In the 1980s; in his teens
D．In 1980’s; in the teens
答案
答案：C
“在二十世纪八十年代” In the 1980s，“在某人几十多岁时”in sb’+岁数名词的复数，所以答案C。