SummarizationRead each of the following short paragraphs and complete the phrase or sentence that expresses the main idea of the paragraph. The first letter of the missing word is given before the blank.Paragraph 4.Engineers at Sandia National Laboratories in Albuquerque have built two different systems that use ultraviolet light from the sun to break up toxic chemicals in water. This is a big improvement over conventional water treatment system, which only filter toxic chemicals out, leaving the problem of disposal.4.New e_______on water treatment.
【正确答案】：experiment
【题目解析】：P162
