设A是一个n阶方阵，已知│A│=2，则│-2A│等于：（）
A.（-2）n+1
B.（-1）n2n+1
C.-2n+1
D.-22
参考答案：B
Look and tick or cross. 看图，判断句子是否与图意相符，相符的打“√”，不相符的打“×”。
( ) 1. This is a duck.
( ) 2. This is a cow.
( ) 3. Fish can swim.
( ) 4. This is a bird.
( ) 5. This is a goat.
思维
