Steven Stein likes to follow garbage trucks.His strange habit makes sense when you consider that he's（11）_____environmental scientist who studies how to reduce garbage， including things that fall off garbage trucks as they drive down the road.What is even（12）_____（interest）is that one of Stein's jobs is defending an industry behind the plastic shopping bag.

Americans use more than 100 billion thin plastic bags every year.So many end up in tree branches or along highways that a（13）_____（grow）number of cities do not allow them at checkouts.The bags（14）_____（prohibit）in some 90 cities in California， including Los Angeles.Eyeing these headwinds， plastic-bag makers are hiring scientists（15）_____ Stein to make the case that their products are not as bad for the planet as most people assume.

Among the bag（16）_____（make）arguments：many cities with bans still allow shoppers to purchase paper bags，（17）_____are easily recycled but require more energy to produce and transport.And while plastic bags may be ugly to look at， they represent a small percentage of all garbage on the ground today.

The industry（18）_____（take）aim at the product that has appeared as its replacement： reusable shopping bags.The stronger a（19）_____（reuse）bag is， the longer its life and the more plastic-bag use it cancels out.However， longer-lasting reusable bags often require more energy to make.One study found that a cotton bag must be used at least 131 times to be better for the planet than plastic.

Environmentalists don't dispute these points.They hope paper bags will be banned someday（20）_____want shoppers to use the same reusable bags for years.

11.an【解析】空后environmental scientist是可数名词，且此处泛指他是一位环境科学家，故填不定冠词an。

12.more interesting【解析】根据空前的even判断此处应填interest的形容词形式，且even修饰比较级，意为“甚至更……”。句意：更有趣的是Stein工作内容之一是保卫一个支持塑料购物袋的行业。

13.growing【解析】根据空前的冠词a及空后的名词number可知，此处需用grow的形容词形式。a growing number of意为“越来越多的”。

14.are prohibited【解析】空格所在句缺少谓语部分，the bags为复数形式且和谓语动词为被动关系，故填are prohibited。

15.like【解析】分析上下文可知，此处句意为“塑料袋制造商雇用像Stein这样的科学家以让人们相信他们的产品对于这个星球不像大部人以为的那么有害”，故填like。

16.makers'【解析】句意：塑料袋_____的论据是：很多有塑料袋禁令的城市仍然允许购物者购买纸袋，纸袋容易回收，但需要更多的能源来生产和运输。分析句意可知，此处应填make的名词形式“制造商”的所有格，且制造商不止一家，故填makers'。

17.which【解析】空格所在句为非限定定语从句，修饰逗号前的 paper bags，且在从句中充当主语。故填which。

18.has taken【解析】句意：这个行业以已经出现的替代品——可重复使用的购物袋为目标。根据句意，这个行业已经以此为目标，需用完成时，且主语为第三人称单数，故填has taken。

19.resuable【解析】根据空前的a及空后的bag判定，此处填reuse的形容词形式，根据复现原则，前后文多次出现reusable，故填reusable。

20.and【解析】此空连接两个并列句子，故填and。