平面曲线y = f(x)垂直渐近线的条数至多是
A. 无数条
B. 1
C. 2
D. 3
Zhuge Liang was born during the __________________ ① Period. He was a famous statesman, ______________________ ②.
In 207, Liu Bei paid three visits to the __________________ ③ of Zhuge Liang.
Zhuge Liang began to assist Liu Bei after the “_____________________” ④.