4. 下面的句子中每个句子都有四处划有横线并标以a、b、c、d，其中有一处是错误的。指出你认为错误之处。（为了整理方便，我省略了a、b、c、d）
1) commercial television has mixed entertainment and advertising, so if you want the entertainment, you have to put up the advertising.
2) if suppose you turn aside from these familiar things and study objects you have to look at through a magnifying glass, you will find many things that will puzzle you.
3) the united states is known for its supermarkets where huge quantities of various kinds of food and household article are sold.
4) experiments have proved that daydreaming is part of daily life and that certain amount each day is essential for maintaining equilibrium.
5) the pioneer type of composer is the characteristic one at the turn of the seventeenth century and also at the beginning of the twentieth century, but it is much less evident today.
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