though it ---hot,she is ---better.

A.
go和become在这里都是系动词,后面跟形容词.区别在于:
go主要指一种由强到弱或由好到坏的变化(可用于人或事物).
如:go insane 发疯,The meat's gone off [gone bad].肉变味(变坏)了.The radio's gone wrong.收音机出毛病了.另外,go还可用于人或事物颜色的变色,与turn用法相同.如：She went [turned] blue with cold.她冻得脸色发青了.
become主要指一个人暂时性的身心变化或永久性的自然变化.
become ill,old,well,deaf,strong,etc (得病,变老,痊愈,变聋,变强,等).
综上分析,应选择A.

A
因为不能说she is going better.所有应选A

b
become hot:变得热起来
go better: 变得更好了