pernicious

这种谣言对社会具有潜移默化的危害性。

Such rumors have a ___pernicious effect on society over time.

这种有害的野草疯狂蔓延，扼杀了本地的野花。

The ___pernicious weed spread aggressively, choking out the native wildflowers.

这种有害的意识形态在在线论坛中传播，慢慢地将心理脆弱的青少年引向极端。

The ___pernicious ideology spread through online forums, slowly radicalizing vulnerable teenagers.