問題詳情：
The truth 61 trees are vital to our life is not a secret. They provide us with food, wood and most 62 (important), oxygen. Now there is one more thing we can add to this list—blocking out harmful bacteria from water.
The discovery 63 (make) by a team consisting 64 scientists from the Massachusetts Institute of Technology (MIT) and high school students 65 were seeking a natural water filter—one that would help communities in developing countries that do not have access to modern water filter systems.
The 66 (research), led by Professor Rohit Karnik, decided to turn to trees for help 67 they could allow liquid to flow through, while blocking out air bubbles.
They began by cutting 1.5-inch-wide sections of tree bark from the branches of a white pine tree. The people related then tested the wood’s filtering ability by pouring water containing red dye particles of different sizes through. 68 their amazement, they found that it was effective in trapping all the articles. 69 (encourage), the team conducted 70 experiment, this time with water that contained bacteria. Sure enough, the sapwood held back 99% of the bacteria, allowing only 1% to flow through.
【回答】
61. that 62 importantly 63 was made 64 of 65who/ that
66 researchers 67 because 68 To 69Encouraged 70 anther
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