chemistry?

A
Since that "the air pressure on both sides would become the same" after opening the stock pock, the height of mercury on both sides would also be the same. As a result, the left side of mercury would rise for h/2, and the right side of mercury would drop for h/2, making the height both h/2. Since h would become smaller (h/2), the answer should be (A).
因為，在打開開關之後“左右兩側的氣壓將變得相同”，所以兩側的水銀高度也將會變得一樣。因此，水銀柱的左邊高度將上升h / 2，並且水銀柱的右邊高度將下降 h / 2，使得兩側的水銀柱高度皆為h / 2。由於h將變小（變為h / 2），所以答案應該是（A）。