Continuity and Change D.7 Reproduction (id: ea397586b)

本题目来源于试卷: Continuity and Change D.7 Reproduction，类别为 IB生物学

[单选题]
The graph shows the level of hormones in a woman's body5+ z gj2:xb*vz(jfbfz durins.d*vvfsa4me u syh9s7 nbu;7ec 127ug pregnancy. Which line on the graph represents the level of human 2eb.m f7sd uv cs eh94u*v; sasuy177nchorionic gonadotropin?

A.
B.
C.
D.


参考答案:  D


本题详细解析:

During pregnancy, the levels of human chorionic gonadotropin (hCG) increase to maintain the corpus luteum in the ovary, so that estrogen and progesterone are secreted to maintain the uterus lining and prevent ovulation. Once the placenta takes over the support of the embryo, hCG levels fall. Choice D is correct.

Choice A is incorrect as it represents estrogen which rises towards the end of pregnancy to promote contractions. Choice B is incorrect as it represents progesterone which decreases towards the end of pregnancy to promote contractions. Choice C is incorrect, as the hormones involved in pregnancy all fluctuate and do not remain stable.

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