Peasants are living a good life because of ? good harvests

Question

A.a set of B.a pair of C.a series of D.a piece of

Answer 1

C.a series of 一连串,一系列
"一系列的丰收使得农民们生活富足"

a set of 一套;一副（家具）
a pair of 一双；一对；一副（裤子/鞋子/袜子/眼镜等由两个组成的一对）
a piece of＋不可数名词 一个/块/条...
a piece of news/paper/cake/chalk
We have a set of table glass.
我们有一套玻璃餐具。
He has a set of ugly furniture.
他有一套难看的家具。
The theory is based on a series of wrong assumptions.
这一理论是以一系列错误的设想为依据的。
A series of mischance happened.
一连串不幸的事发生了。
A series of propaganda activity.
一系列的宣传活动。
I want to buy a pair of pants.
我想买一条长裤。
I want a pair of sports shoes.
我想要一双运动鞋。
The baby was given a piece of candy.
这孩子拿到了一块糖。
I'd like a piece of chocolate.
我想要吃块巧克力。
Please give me a piece of pie.
请给我一张馅饼。

Answer 2

我觉得该选C.series的意思是一连串，一系列的。
整体可以翻译：为农民依靠一连串的丰收，获得了美好的生活。
o(∩_∩)o...，这是我的个人理解，不知道对错。