Though he sometimes complains bitterly of it, he would not, ______, exchange it for the mo

Though he sometimes complains bitterly of it, he would not, ______, exchange it for the more predictable climate of other lands.

A．since he can

B．even if he could

C．although he should

D．but he could

请帮忙给出正确答案和分析，谢谢！