问题补充：
The reason why this kind of machine is popular with users is that it will work in temperature.
A. official
B. extreme
C. common
D. natural
答案：
A. official
(答案→)B. extreme
C. common
D. natural
解析：A. official官方的 B. extreme极限的C. common 普遍的 D. natural自然的；句意：为什么这种机器对用户来说是流行的，是因为它能工作在极限的温度下。故选B
