你好想问你一道题，这个空为何是That？
________ each large firm will act with consideration of its own needs and thus avoid selling its products for more than its competitors charge is commonly recognized by advocates of free-market economic theories.
that 引导一个陈述性质的主语从句。这么长的主语从句，一般用形式主语it 代之，然后外置：
Thateach large firm will act with consideration of its own needs and thus avoid selling its products for more than its competitors chargeis commonly recognized by advocates of free-market economic theories.
变为：
It is commonly recognized by advocates of free-market economic theories thateach large firm will act with consideration of its own needs and thus avoid selling its products for more than its competitors charge.
【注】划线部分为主语从句。
