一些水果和蔬菜中含有能防止和治疗坏血病的物质——维生素C，维生素类物质在人体消化

商务谈判背景调查包括（）、（）和（）。

Footracing(竞走)is a popular activity in the United States．It is not only seen as a competitive sport，but also as a way to exercise，and to donate(捐赠)money to a good cause．Though serious runners may spend months training to compete，other runners and walkers might not train at a11．Those not competing to win might run in an effort to beat their own time，or simply to enjoy the fun and exercise．People of all ages, from those less than one year old to those in their 80s, enter into this sport．The races are held on city streets，on college campuses，through parks，and in suburban areas，and commonly 5 to 1 0 kilometers in length．

The largest footrace in the world is the 1 2-kilometer Bay to Breakers race that is held in San Francisco every spring．This race begins on the east side of the city near San Francisco Bay and ends on the west side at the Pacific Ocean．In 1 993 there were 80，000 people running in this race through the streets and hills of San Francisco．In the front are the serious runners who compete to win，and who might finish in as little as 34 minutes．Behind them are the thousands who take several hours to finish．In the back of the race are those who wear costumes just for fun．In 1 993 there was a group of men all of whom dressed up like Elvis Priestly．There was a group of firefighters who were all tied in a long line and were carrying a fire—hose(水龙带)．One year there was a wedding party in which the bride dressed in a long white gown(长袍)and the groom wore a tuxedo(晚礼服)．They threw flowers to by-standers，and were actually married at some point along the route．

小题1:The main purpose of this text is to__________．

A．describe a popular activity

B．encourage people to exercise

C．make fun of runners in costume

D．give reasons for the popularity of footraces小题2:Which of the following is implied by the author?

A．Walkers don’t compete for prizes．

B．Footraces appeal to a variety of people．

C．Entering a race is a way to make friends．

D．Running is a good way to strengthen the heart．小题3:The underlined words “to a good cause” in the first paragraph could best be replaced by ___________.

A．for a good reason

B．to support a sound principle

C．for a good purpose

D．to protect an excellent player

在LAE1型辅锅炉燃烧时序控制系统中，燃烧锁定指示灯L2亮的条件为（）

A.负荷继电器AR通电

B.燃烧锁定继电器BR通电

C.在正常燃烧阶段

D.风机因故障停转时

《合同法》规定，当事人订立合同应具有要约邀请、要约和承诺三个阶段。 ( )

脱脂准备药物是什么？