答案是选 B.seldom是很少的意思,if ever是习惯省略句,类似的还有if so,if possibel,if necessary等等.省略了主谓if it is possible等.seldom,if ever这里本意是,if he has ever refused them.省略成了if ever,译为：他只是准备帮助别人,如果曾经拒绝过他们,那也是很少的.