bob went to bed at 10 o'clock.his mother came back home at 10 o'clock 合并成一句话

bob went to bed at 10 o'clock.his mother came back home at 10 o'clock 合并成一句话
bob went to bed at 10 o'clock.his mother came back home at 10 o'clock 合并成一句话

bob went to bed at 10 o'clock.his mother came back home at 10 o'clock 合并成一句话
bob didn't go to bed until his mother came back home at 10 'clock(bob直到他妈妈十点回来才上床睡觉)或者bob went to bed when his mother came back home at 10 'clock（bob 当他妈妈十点回来的时候上床睡觉）