单选题

NSArray *array = [NSArray arrayWithObjects:@"1",@"2",@"3",@"4",@"2", nil]; NSMutableSet *set = [[NSMutableSet alloc]init]; for(NSString *str in array) { [set addObject:str]; } NSLog(@"%lu",[set count]); [set release]; 控制台打印的结果是：

Question

A. 4

B. 5

C. 6

D. 7