I think this is a great idea.
I think this is a good idea.
Did you think the lesson difficult?
Let us think about the matter deeply.
I think there is a problem with the TV.
Let us think about our future carefully.
I think there is a problem with the food.
I think there is a problem with the shirt.
I think there is a problem with the drink.
Did you think the English grammar class difficult?
At first I thought it went well, but now that I've had some time to think about it, maybe it wasn't that great after all.
They asked me to describe a situation where I had to make an unpopular decision. I couldn't think of anything on the spot.