If you run a business and have capital gains to report, you should file ITR3. This is because, those who have business income cannot use ITR1, ITR2. So for an individual, this leaves only ITR3 and ITR4.
However, ITR4 cannot be used when there is Income under the head ―Capital Gains‖, e.g. Short-term capital gains or long-term capital gains from the sale of house, plot, shares etc.
Other conditions when ITR is not applicable, see: Which ITR Form Should I use for A.Y. 2019-20?