The word with a negative connotation is discouraging.
When someone is discouraged, they are dispirited, disheartened, and with a lack of enthusiasm; this has a negative implication.
All other options have positive connotations, except maybe bulb, which is pretty neutral.
I hope this helps you!
Answer:
let us not wallow in the valley of despair.
The subordinate clause is "you must start researching now"
