English Synonyms Practice Test 5

Slow : moving or operating, or designed to do so, only at a low speed; not quick or fast.
Treacherous : guilty of or involving betrayal or deception.
Pessimistic : tending to see the worst aspect of things or believe that the worst will happen.
Unfortunate : having or marked by bad fortune; unlucky.
Insidious : proceeding in a gradual, subtle way, but with very harmful effects.

Synonym of Insidious is Treacherous