根据汉语意思完成句子，每空只填一词。
小题1:昨天中午妈妈做饭的时候，我的小妹妹正在玩游戏。
My little sister was playing games _________ my mother was cooking at noon yesterday.
小题2:毫无疑问, 由于计算机的出现, 我们的世界正变得越来越小。
There’s no ________ that our world is becoming smaller and smaller because of the appearance of computers.
小题3:杰克喜欢收到别人的来信，但他从不给别人写信。
Jack likes __________ __________ others , but he never writes to others .
小题4:如果明天不下雨， 我们就会去野餐。
If it _______   ________ tomorrow, we will have a picnic.