1. Is that your opinion? Is that what you think? Are you sure?
do you think so?
This is a phrase used to challenge or invite an opinion. It is a popular expression you will often hear in many contexts and scenarios. This phrase is often shortened to 'you think?'. Sometimes a word such as 'really' can be added for emphasis: "You said taxes will come down next year. Do you really think so?" You are more likely to hear this phrase used in social or conversational contexts.