"I think", "I think that", "I imagine" or "I imagine that"

[Rachel Adams]

"I think", "I think that", "I imagine" or "I imagine that"

Is it wrong to use "that" after these verbs in my sentence?

"I think/imagine that smoking is bad."

 

[emsr2d2]

Re: "I think", "I think that", "I imagine" or "I imagine that"

It's not wrong but it's not necessary.