他迟到的借口很薄弱，没有说服力。

His excuse for being late was ___weak and unconvincing.

没有足够的证据，她的论点显得很弱。

Without sufficient evidence, her argument appeared ___weak.

委员会因推理薄弱而拒绝了该提案。

The committee rejected the proposal due to its ___weak reasoning.