It's never too old to learn.Karl Marx began to learn English in his ________.
A．the fiftieth B．fiftieth C．fifty D．fifties
It's never too old to learn.Karl Marx began to learn English in his ________.
A．the fiftieth B．fiftieth C．fifty D．fifties
D “in＋one's＋整十基数词复数”表示“在某人几十多岁时”，故选D。