为了解乙肝在某地发病情况，小王走访了当地卫生防疫站和多家医院。小王的这种科学探究方法是 [ ]
A．观察法
B．调查法
C．实验法
D．比较法
B
I want to play football, but I am hungry. I ______________ eat some food.[ ]
A. have to
B. can
C. would like
土壤退化
