Questions

International Day for Disaster Reduction, held every 13 October, celebrates how people and communities around the world are reducing their exposure to disasters.

The year 2017 focus is : Reducing the number of affected people by disasters by 2030.

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.

Vitamin B12 is the only water-soluble vitamin that can be stored in the liver for many years. There are 9 water soluble vitamins.

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.

By trial and error method,

P=0, Q=9, R=0 satisfies the values.