The most suitable chemical which can be applied to the water surface for reducing evaporation is________?

If an activity has its optimistic, most likely and pessimistic times as 2, 3 and 7 respectively, then its expected time and variance are respectively________?

Which one of the following gases is most significant as air pollutant?

A 2 m long ladder rests against a wall and makes an angle of 30° with the horizontal floor. Where will be the instantaneous center of rotation when the ladder starts slipping?

Which of the following is used for servicing and repairs of the aircraft?

Dried sewage after treatment is used as________?