His friends are not happy with him because he always turns down their invitations（ ）ill health.
A、
on the ground of
B、
on the strength of
C、
in view of
D、
by means of
【正确答案】：A
【题目解析】：
A.on the ground of：以...为理由；B.on the strength of：基于，凭借；C.in view of：鉴于，考虑到；D.by means of：用，依靠，空格前面为拒绝他们的邀请，后面为生病，所以应该是选A。句意：他的朋友们对他不满意，因为他总是以健康不佳为由拒绝他们的邀请。