One of California' s greatest problems is providing ______ water to meet the needs of its expanding population.

单项选择题The war has raised questions about the utility of the national guard and reserve organizations, which the Department of Defense finds ______ to U.S. defense needs but which the Congress desires to maintain.

单项选择题The ______ homogeneous Dakota grasslands are actually a botanical garden (植物园) of more than 400 types of grasses.

单项选择题It is ______ whether Sam will come to attend his best friend's funeral as he has taken the town's money and made off with it.

单项选择题It is well known that knowledge is the ______ condition for expansion of mind.

单项选择题Travelers in space have to ______ many discomforts in their spaceships.

单项选择题Congress was hit with a ______ mail campaign, and nearly 150 bills were introduced which would amend the Constitution to permit Bible reading and prayer in public places.

单项选择题The production of synthetics intensified the drain on energy resources, already sorely pressed by the increase in ______ demand.

单项选择题Moving down the hills and around the curves, the ______ of cars was not able to proceed faster than twenty miles an hour.

单项选择题Smoking should be banned in public places and great efforts should be made to inform young people of the ______ consequences of taking up the habit.

单项选择题Which of the following is TRUE according to the passage