单选题

运行以下代码： NSString * str = @" &nb...

Question

运行以下代码：
NSString * str = @"   I am a boy!   "
NSString *temptext = [str stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]]
NSLog(@"%@", temptext)
temptext结果为______________________________

A. "I am a boy!"

B. "Iamaboy!"

C. "I"

D. ""