假設題目是:Eating less and doing exercises are important to our health. 要以虛主詞為句首，是改成 It is important to our health to eat less and do exercises. 還是 They are important to our health to eat less and do exercises. 補習班老師說，因為這兩件事視為一個虛主詞，所以用it開頭? 所以虛主詞放句首((不論幾件事))都只會用it做開頭?