A:described; wouldn’t waste
B:had described; wouldn’t have wasted
C:would have described; had wasted
D:described; wasted
B: I'm going to____.
根据所给单词,连成完整的句子。
如图,⊙O的半径为4,PC切⊙O于点C,交直径AB延长线于点P,若CP长为4,则阴影部分的面积为 ____ 。
铅及其化合物可用于蓄电池,耐酸设备及X射线防护等.回答下列问题: