Calculate the density of xenon gas at a pressure of 753 mmHg and a temperature of 43 ºC. Express the density to three significant figures and include the appropriate units.

The answer to this is the 3rd choice!

The water cycle increase the water content in the earth atmosphere

The population of unionid mussels decreased after zebra mussels were introduced. zebra mussels competed with the unionid mussels for food. the zebra mussels were able to displace the unionid mussels, allowing the zebra mussel population to increase  over the years. the unionid mussel population decreased because  of lack of food.