He won't____ ____ ____to Hangzhou because of the weather.
——He on the phone.
What's this? ____ Her name is Li Li.
Hello, Jenny.____ I'm fine.
What's her name?____ I have four.
How many books do you have?____ It's a cat.
How are you?____ Hi, Wang Hong.
已知发电机线圈面积S=10cm2,总匝数n=20匝,求匀强磁场的磁感应强度大小B;