皮皮学，免费搜题
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搜题
【单选题】
利用接种疫苗预防传染病，其作用主要是A.
消灭传染源
B.
切断传播途径
C.
提高动物抵抗力
D.
提高动物的易感性
拍照语音搜题，微信中搜索"皮皮学"使用
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参考解析：
知识点：
皮皮学刷刷变学霸
举一反三
【单选题】Johnny cried bitterly , not even attempting to _______ the tears.
A.
hold out
B.
hold on
C.
hold back
D.
hold in
【简答题】How did ancient people remember their knowledge of weather patterns? They ______.
【简答题】Johnny cried ______ in the classroom, not even ______ to ______ ______ the tears.
【简答题】What helped ancient people forecast the weather? By observing the sky, ______.
【判断题】焊接温度为260°C,3秒。温度过高,时间过长会烧坏芯片。为了更好地保护LED,LED胶体与PC板应保持1mm以上的间距,以使焊接热量在引脚中散除。( )
A.
正确
B.
错误
【单选题】People living in the desert choose to keep their ancient lifestyles and customs, _______people in cities throw away their cultural traditions.
A.
when
B.
if
C.
unless
D.
while
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