()为鳊属鱼类。
A.刺鳊
B.华鳊
C.长春鳊
D.拟刺鳊鮈
参考答案:C
{(x,y)|0≤x≤2,0≤y<2,x,y∈N}中共有 ______个元素.
We should help her when she is ().
A.in trouble
B.in a trouble
C.in the trouble
D.in troubles