A、F = AB+<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1551347104991c84f2fa2ee234354acb1c95817676b35image15.png" style="width:24px;height:18px;">
B、F=<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/155134710503659d74e14c61746f7914a7297a660e7f2image16.png" style="width:25px;height:18px;">+AB
C、F= <img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/1551347105092878da59dcf9947b6b68784e81ff271d6image15.png" style="width:24px;height:18px;">+<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/examination/imgUplod/15513471051580184bdad7c15421ba96b123ea0e589bcimage16.png" style="width:25px;height:18px;">