Questions

Pyrenees, a chief mountain in Europe, forms a part of the great mountain across Europe and Asia.

Caffeine is also a psychoactive drug which alters the mood and conscious in our behaviour. It is widely consumed as a psychoactive drug.

Black  surfaces are good emitters of heat ( They are also good absorbers of heat). If the black surface is rough too, the emitting will be better. So (b) is the correct answer. Shining surfaces reflect back radiation. So if the black surface is also shining the effectiveness of emitting heat is lessened.

Can’t delete a row from primary table if there are related rows in secondary table.

The main purpose of balancing chemical equations is to make the mass of reactants is equal to mass of products obtained after the reaction. Hence, to make law of conservation of mass is purpose of balancing chemica equations.