Gary Locke , a Chinese-American, once______ as the governor of Washington for 8 years and now is U．S．Commerce Secretary．

A．had worked

B．worked

C．is working

D．has been working

最常见的非生物混浊是蛋白质混浊，啤酒的蛋白质混浊包括两种情况：冷混浊（也称可逆性混浊）和（）（也称不可逆混浊）。