Question

Mary's mother looks so young that it is hard to imagine she is already in her ________ (四十).

Answer

forties

【解析】

句意：玛丽的母亲看上去很年轻，很难想象她已经四十多岁了。

“四十”在英文中表示为“forty”，in+one’s+基数词复数，表示“在某人几十多岁时”，根据“she is already in her _______”，结合所给中文，可推测出此处是“forties”，故答案为forties。