An unusually attractive little thing, and as strong as a heifer

An unusually attractive little thing, and as strong as a heifer in （ ）.
A、living
B、collect
C、appearance
D、them
【正确答案】：C
【题目解析】：该段选自上册课文Lesson 3: The Use of Force。本句意为：这是一个非常惹人喜爱的小东西，外表长得像小牛一样结实。