43．Instead of trying to keep down the body temperature deep inside thebody, which would involve the expenditure of water and energy，desert mammals allow theirtemperatures to rise to what would normally be fever height，and temperatures as high as 46degrees Celsius have been measured in Grant's gazelles．

(what引导的从句作rise to的宾语)

沙漠哺乳动物并不试图将体温控制得很低，因为这么做将会涉及水和能量的消耗，而是允许体温上升到平常是高烧的温度——有人在格兰特羚羊身上曾测到高达46摄氏度的体温。

分句1：Instead of trying to keep down thebody temperature deep inside the body

分句2：which would involve the expenditureof water and energy

分句3：desert mammals allow theirtemperatures to rise to

分句4：what would normally be fever height

分句5：and temperatures as high as 46degrees Celsius have been measured in Grant's gazelles．

分句3、5是整个长句子的主句

分句2是分句1的定语从句

分句4是3的宾语从句。

1和2嵌套

1、2和3嵌套

3和4嵌套

3、4和5并列