A.compulsory
B.optional
C.free
D.expensive
第1题:
A. pay
B. paid
C. to pay
D. paying
第2题:
It was _____ last year ______ he came to realize the importance of learning English.
A、until ; before
B、that ; until
C、until ; that
D、before ; until
第3题:
第4题:
None of us are invited to ( ) international Fair this year.
A.attend to
B.tend
C.tend to
D.attend
第5题:
Consider the query:Mysql> SET @run = 15;Mysql> EXPLAIN SELECT objective, stage, COUNT (stage)FROM iteminformationWHERE run=@run AND objective=’7.1’GROUP BY objective,stageORDER BY stage;The iteminformation table has the following indexes;Mysql> SHOW INDEXES FROM iteminformation:This query is run several times in an application with different values in the WHERE clause in a growing data set.What is the primary improvement that can be made for this scenario?()


A.Do not pass a user variable in the WHERE clause because it limits the ability of the optimizer to use indexes
B.Add an index on the objective column so that is can be used in both the WHERE and GROUP BY operations
C.Drop the run_2 index because it has caused a conflict in the choice of key for this query
D.Execute the run_2 index because it has caused a conflict in the choice of key for this query
E.Add a composite index on (run,objective,stage) to allow the query to fully utilize an index
第6题:
酚醛树脂按照反应分为三个阶段,不属于的是
A.甲阶(A-stage)
B.乙阶(B-stage)
C.丙阶(C-stage)
D.D 丁阶(D-stage)