问题 选择题

测得生活中一些物质的pH如下表,下列说法错误的是

   物质肥皂水食盐水 唾液 柠檬汁洗涤剂
    pH  lO.2  7.0  6.8  2.5 12.2
A、食盐水是中性物质     B、肥皂水能使蓝色石蕊试纸变红

C、柠檬汁的酸性比唾液强  D、洗涤剂能使无色的酚酞试液变红

答案

答案:B

肥皂水是碱性的,石蕊遇酸变红遇碱变蓝,食盐水是中性的,唾液和柠檬汁是酸性的,洗涤剂碱性的。酚酞遇酸不变色,遇碱变红。B错误。

单项选择题

By almost every measure, Paul Pfingst is an unsentimental prosecutor. Last week the San Diego County district attorney said he fully intends to try (1) Charles Andrew Williams, 15, as an adult (2) the Santana High School shootings. Even before the (3) Pfingst had stood behind the controversial California law that (4) treating murder suspects as young as 14 as adults.

So nobody would have wagered that Pfingst would also be the first D. A. ( district attorney) in the U. S. to (5) his very own Innocence Project. Yet last June, Pfingst told his attorneys to go back over old murder and rape (6) and see ff any unravel with newly developed DNA-testing tools. In other words, he wanted to revisit past victories—this time playing for the other team. "I think people misunderstand being conservative (7) being biased," says Pfingst. "I consider myself a pragmatic guy, and I have no interest in putting (8) people in jail."

Around the U. S. , flabbergasted defense attorneys and their jailed clients cheered his move. Among prosecutors, (9) , there was an awkward pause. (10) , each DNA test costs as much as $ 5,000. Then there’s the (11) risk: if dozens of innocents (12 , the D.A. will have indicted his shop.

(13) nine months later, no budgets have been busted or prosecutors ousted. Only the rare case merits review. Pfingst’s team considers convictions before 1993, when the city started (14) DNA testing. They discard cases if the defendant has been released. Of the 560 (15) files, they have re-examined 200, looking for cases with biological evidence and defendants who still (16) innocence.

They have identified three so far. The most compelling involves a man (17) 12 years for molesting a girl who was playing in his apartment. But others were there at the time. Police found a small drop of saliva on the (18) shirt—too small a (19) to test in 1991. Today that spot could free a man. Test results are due any day. (20) by San Diego, 10 other counties in the U.S. are starting DNA audits.

17()

A.observing

B.serving

C.sentencing

D.inhabiting

单项选择题