princess

2.好像是说when没有 介词＋which 来得指代明确

princess

关于number和amount的区别(Merriam-Webster)：
Number is regularly used with count nouns
  eg:a large number of mistakes; any number of times
while amount is mainly used with mass nouns
  eg:annual amount of rainfall; a substantial amount of money

The use of amount with count nouns has been frequently criticized; it usually occurs when the number of things is thought of as a mass or collection
  eg:glad to furnish any amount of black pebbles     New Yorker
   a substantial amount of film offers               Lily Tomlin
or when money is involved
  eg:a substantial amount of loans                   E. R. Black