Answer:
d. A water particle and an air particle
Explanation:
The force of gravity (F) between two objects of masses m1 and m2 and separated by a distance r is given as:

where G is the gravitational constant
This force is therefore, directly proportional to the masses and inversely related to the distance between them.
Based on the given options, since the masses of the water and air particles are very small (masses of earth, moon and sun is relatively huge), the gravitational force between them would be negligible and difficult to measure.
Sucrose is insoluble in dichloromethane because dichloromethane is not a polar solvent.
Sucrose is soluble in water because the molecules of sucrose has the ability to react with the molecules of water and thereby forming hydrogen bond which enhance the dispersion of sucrose in the water.
Sugar can not react in a similar way with dichloromethane because they do not possess chemical species that can react together to form bonds. Thus, sugar is a polar substance which can not dissolve in a non-polar solvent.
The appropriate answer is b. greenhouse gases. Greenhouse gases such as carbon dioxide and methane have the ability to trap infrared radiation or heat in the atmosphere. Without these gases the Earth would be thirty degrees cooler than it is today. Pollution today has caused more of these gases to enter the atmosphere and this is the main cause of contemporary global warming.
Ozone in the stratosphere actually blocks another form of radiation called ultraviolet radiation. Geothermal energy is derived from hot rocks inside the earth.