So far there is no proof ______ spaceships from other planets do exist.
A.which
B.that
C.how
D.what
The passage tells us that proof of life on Mars would ______.
A.make clear the complex chemistry in the development of life
B.confirm the suggestion that bacterial fossils traveled to Earth on a meteor
C.reveal the kind of conditions under which life originates
D.provide an explanation why life is common in the universe
A.与安慰剂相比,鲑降钙素100IU能明显降低对非椎体骨折风险
B.与安慰剂相比,鲑降钙素100IU能明显降低新发椎体骨折风险
C.与安慰剂相比,鲑降钙素200IU能明显降低新发椎体骨折风险
D.与安慰剂相比,鲑降钙素200IU能明显降低非椎体骨折风险
A.安全解用于泄放可燃液体时,宣将排泄管接入事故储槽、污油罐或其他容器
B.当安全阀的入口处装有隔断阀时,隔断阀必须保持常开状态并加铅封
C.波化气体容器上的安全阀应安装于液相部分,防止排出气体物料,发生事故
D.室内可燃气体压缩机安全阀的放空口宜引出房顶,并高于房顶2m以上