用所给动词的正确时态填空:1.my watch( )(drop)out of my pocket when I was on my way to school.2.
we'll go out for a picnic if it( )(not rain)tomorrow.3.that's the family whose house( )(burn)down.4.as I was walking along the river,it( )(begin)to rain.5.every time she( )(come)here,she will buy me something nice.6.don't( )(waste)electricity.we should( )(turn)off the lights when we leave the room.