单项选择题
A．wholly effective, but typically ignored
B．inexpensive, but insufficiently useful
C．promising, but difficult to implement
D．necessary, but likely to produce ill side-effects
E．universally accessible, but unnecessary
单项选择题 The primary purpose of the passage is to（）
单项选择题 The passage implies that the strain on freshwater aquifers caused by poor irrigation patterns may be reduced by all of the following methods EXCEPT（）
单项选择题 It can be inferred from the passage that low-pressure sprinklers would be more preferable to high-pressure models for which of the following reasons（）