—How often do I need to feed the birds?

—They ________ food every day，or they will be hungry.

A．must give

B．mustn’t give

C．must be given

D．mustn’t be given

条件响应交互类型是在执行图标前后判断条件，如果条件满足，则执行所属图标，判断的条件和图表的名称相同。