________ is known to us all is that the old worker, for _______ life was hard in the past, still works hard in his seventies.

A．As; whom

B．What; whose

C．It; whose

D．What; whom

预防鸡马立克氏病的火鸡疱疹病毒疫苗属于（）

A、灭活疫苗

B、核酸疫苗

C、异源疫苗

D、亚单位疫苗