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【单选题】
新药经批准进入了临床试验阶段,III期临床试验的病例数( )。A.
20~30例
B.
不少于100例
C.
不少于200例
D.
不少于300例
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举一反三
【单选题】On a half-duplex Ethernet LAN, two hosts attempt to send data simultaneously,resulting in a collision. Following this collision, what will the hosts do?（）
A.
The destination host sends a request to the source for retransmission.
B.
The jam signal indicates that the collision has been cleared.
C.
The hosts will attempt to resume transmission after a time delay has expired.
D.
An electrical pulse indicates that the collision has cleared.
E.
The router on the segment will signal that the collision has cleared.
F.
The hosts will do nothing, as the higher layers are responsible for data error correction and re-transmission.
【单选题】在pH＝0的无色透明溶液中，因发生氧化还原反应而不能大量共存的离子组是（ ）
A.
Na + 、K + 、MnO 4 — 、Cl —
B.
Cl — 、SO 4 2— 、K + 、Na +
C.
Na + 、Cl — 、CH 3 COO — 、K +
D.
K + 、I — 、Na + 、ClO —
【简答题】A signal source has an open-circuit voltage of 10mV and a short-circuit current of 10μA. The source resistance is kΩ
【单选题】On a half-duplex Ethernet LAN, two hosts attempt to send data simultaneously, resulting in a collision. Following this collision, what will the hosts do? (Select all valid answers)
A.
The destination host sends a request to the source for retransmission.
B.
The jam signal indicates that the collision has been cleared.
C.
The hosts will attempt to resume transmission after a time delay has expired.
D.
An electrical pulse indicates that the collision has cleared.
E.
The router on the segment will signal that the collision has cleared.
F.
The hosts will do nothing, as the higher layers are responsible for data error correction and re-transmission.
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