Most organs are formed during the 1st Trimester of pregnancy
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One advantage of mother’s milk to the baby is rich source of docosahexaenoic acid.
A. 对
B. 错
The foods pyramid for older adult is wider than that for the young adults
A. 对
B. 错
Dehydration is not a big concern of the older adults
A. 对
B. 错
正弦交流电压u=220sin(ωt-40°)V的有效值相量为。
A. 220/-40°V
B. 155.6/-40°V
C. 220/40°V
D. 155.6/40°V
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