Which of the following oxides is acidic in nature?

Reaction of $NaCl$ with conc. $H_2SO_4$ liberates a gas,$X$ that turns moist blue litmus paper red. When gas $X$ is passed into a test tube containing egg shell powder suspended in water,another gas,$Y$ is generated which when passed through lime water makes it milky. The gases $X$ and $Y$,respectively,are

Which of the following is a metalloid?

Which of the following halides does not hydrolyse at room temperature?

When lead nitrate is heated,it gives

In which allotrope of carbon does each carbon atom form four bonds with other carbon atoms?