皮皮学，免费搜题
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【单选题】
非周期信号的幅度频谱是( )。A.
连续的
B.
离散的，谱线正负对称排列
C.
跳变的
D.
离散的，谱线均匀排列
拍照语音搜题，微信中搜索"皮皮学"使用
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知识点：
皮皮学刷刷变学霸
举一反三
【单选题】下面有关免疫的叙述不正确的一项是( )。
A.
免疫指机体对外源性或内源性异物进行识别、排斥和清除的过程
B.
免疫是动物在长期进化过程中形成的一种生理性保护功能
C.
抗御各种病原微生物及其产物对机体的损害属于防御保护
D.
及时监视和排除体内出现的肿瘤细胞属于自身稳定
E.
消除机体内损伤的、衰老和死亡的自身细胞属于自身稳定
【单选题】— When did you become a volunteer? — Two years ago. I _____this group since then. [ ]
A.
have joined in
B.
have taken part in
C.
have been in
D.
have been to
【单选题】You founded your own firm three years ago. You initially contributed $200,000 of your own money and in return you received 3 million shares of stock. Since then, you have sold an additional 2 million ...
A.
50%
B.
40.0%
C.
60.0%
D.
100%
【单选题】You founded your own firm three years ago. You initially contributed $200,000 of your own money and in return you received 3 million shares of stock. Since then, you have sold an additional 2 million ...
A.
50%
B.
40.0%
C.
60.0%
D.
100%
【单选题】—When did you become a volunteer? —Two years ago. I _______ this group since then. [ ]
A.
have joined in
B.
have joined to
C.
have been in
D.
have been to
【简答题】You will hear a sentence and are required to write it down in your exercisebook. The , . Since then, campaigners have mobilized .
【简答题】And what jobs ____________ (you/have) since then?
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