[单选题]在下面几种调速回路中，中的溢流阀是安全阀。
A.定量泵和调速阀的进油节流调速回路
B.定量泵和旁通型调速阀的节流调速回路
C.定量泵和节流阀的进油节流调速回路
D. 以上都不对

2009年9月20日，第二届全国道德模范评选揭晓。这次表彰的全国道德模范都是我们身边的普通人。其中，有精心侍奉婆婆64年的村民张公兰；捡到20万元现金，原封不动交给警方归还失主的保洁员郑仁东；坚守在大河边，无偿为来往的乡亲摆渡49年的村民赵永录；徒步在雪山峡谷邮路穿梭20余万公里，没有延误过一个邮班的乡邮员尼玛拉木……
党和政府一贯高度重视道德建设：2001年，中央颁布了《公民道德建设实施纲要》；2003年，中央确定每年9月20日为“公民道德宣传日”；2007年9月，中央文明办等部门联合评选表彰了首批全国道德模范；同年10月，十七大进一步强调，要加强社会公德、职业道德、家庭美德、个人品德建设。道德是事关国家发展、社会和谐、你我幸福的重要力量。在全社会形成助人为乐、扶贫济困、礼让宽容的道德风尚，是我们建设和谐社会的重要任务。

Passage Three
Space is a dangerous place, not only because of meteors but also because of rays from the sun and other stars. The atmosphere again acts as our protective blanket on earth. Light gets through, and this is essential for plants to make the food which we eat. Heat, too, makes our environment endurable. Various kinds of rays come through the air from outer space, but enormous quantities of radiation from the sun are screened off. As soon as men leave the atmosphere they are exposed to this radiation but their spacesuits or the walls of their spacecraft, if they are inside, do prevent a lot of radiation damage.
Radiation is the greatest known danger to explorers in space. The unit of radiation is called "rem". Scientists have reason to think that a man can put up with far more radiation than 0.1 ream without being damaged; the figure of 60 rems has been agreed on. The trouble is that it is extremely difficult to be sure about radiation da
A. the Apollo mission was very successful
B. protection from space radiation is no easy job
C. astronauts will have deformed children of grandchildren
D. radiation is not a threat to well protection space explorers