新租客在搬进来之前需要签署一份租赁合同。

The new ___tenant needs to sign a lease agreement before moving in.

新租户需要在下周一之前签署租赁合同。

The new ___tenant needs to sign the lease agreement by next Monday.

他担任这个研究项目的首席研究员已有五年。

He has been the principal ___investigator of this research project for five years.