判断下面的计算是(√)否(×)正确。

( ) 1. three + four －five = two

( ) 2. five + four －three = four

( ) 3. six + two －four = five

( ) 4. nine + five －two = seven

( ) 5. seven + one －four = four

目前，EDFA的输出功率一般为（）。

A.1dBm~5dBm

B.5dBm~10dBm

C.10dBm~20dBm

D.20dBm~30dBm