The primitie mouth, or stomodeum, is a slight depression on the surface of the ectoderm.
原始
口(或口凹)是外胚层表面
一个

凹陷。
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秘密
力真题精
About 700,000 children in Mexico dropped out of school last year as recession-stricken families pushed kids to work, and a weak economic recovery will allow only a slight improvement in the drop-out rate in 2010, a top education official said.
高级教育官说,墨西哥去年大约有700,000个孩子因为受经济不景气
影响而被家人逼去工作,
弱
经济复苏将对2010年
辍学率只带来轻
好转。
力真题精
Though it's not known exactly where the mutated virus first appeared, it was first identified in South Africa, and the doctor who made that identification says omicron symptoms were quote " extremely mild" in the initial patients she saw.
尽管目前还不知道变异病毒首次出现
确切位置,但它首先在南非被发现,并且,发现它
医生指出,她最早见到
类患者只表现出“极其轻
”
症状。