A list of words is given in a box. Use appropriate words to fill up the blanks in the following statements

Air, oxygen, wind, water vapour, mixture, combination, direction, road, bottles, cylinders.

(a) The ______ makes the windmill rotate.

(b) Air is a ______ of some gases.

(c) A weather cock shows the ______ in which the air is moving at that place.

(d) Mountaineers carry oxygen ______ with them, while climbing high mountains.