题目

Every summer thousands of Americans stay at home instead of going on holiday because they’re overweight．They don’t want people to see them sunbathing and they don’t want to have to squeeze into plane seats．But now, thanks to the growing number of weight-friendly holiday packages，the overweight are having their days in the sun．  “Overweight people will have a great time on our holidays as we don’t judge them like other people do，”said Liz Nickels，owner of Big Adventures，a US-based company that hosts scuba-diving—a sport of swimming underwater while breathing through在测定胃蛋白酶活性时，将溶液的pH由10降到2的过程中，胃蛋白酶的活性将(    ) A.不断上升　　　　 B.没有变化　　    C.先升后降　　    D.先降后升