单选题 The pop operation ()of the stack..
A. removes an item from the top
B. removes an item from the bottom
C. adds an item to the top
D. adds an item to the bottom
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单选题 The push operation () of the stack.
A. removes an item from the top
B. removes an item from the bottom
C. adds an item to the top
D. adds an item to the bottom
单选题 In a queue, data are inserted only at the()and deleted only at the ().
A. rear; front or rear
B. front; rear
C. rear; front
D. rear or front; front
单选题 The indegree of () of a tree is always zero.
A. any node
B. a branch
C. the root
D. a leaf
单选题 If an internal node has 4 outdegree branches, its degree is ().
A. 9
B. 1
C. 4
D. 5
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