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【单选题】
.. Department of Homeland Security and CIA produced ______ joint report on Monday warning that ______ next 911 could in fact occur on ______ different date.A.
the; a; the
B.
a; the; a
C.
/; the; the
D.
a; /; the
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【多选题】What is the feature of the de novo pathways for purine and pyrimidine biosynthesis?
A.
The de novo pathways for purine and pyrimidine biosynthesis seem to be nearly identical in all living organisms.
B.
Notably, the free bases guanine, adenine, thymine, cytidine, and uracil are not intermediates in these pathways; that is, the bases are not synthesized and then attached to ribose, as might be expected.
C.
The purine ring structure is built up one or a few atoms at a time, attached to ribose throughout the process. The pyrimidine ring is synthesized as orotate, attached to ribose phosphate, and then converted to the common pyrimidine nucleotides required in nucleic acid synthesis.
D.
Although the free bases are not intermediates in the de novo pathways, they are intermediates in some of the salvage pathways.
【简答题】房屋的日常维护可分为()和()两种类型。
【简答题】Cu(s)｜CuSO4(m)｜CuSO4(m')｜Cu(s)浓差电池，m较小的一端为正极。