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【简答题】
某学生利用酪素培养基平板筛选产胞外蛋白酶细菌,在酪素培养基平板上发现有几株菌的菌落周围有蛋白水解圈,是否能仅凭蛋白水解圈与菌落直径比大,就断定该菌株产胞外蛋白酶的能力就大,而将其选择为高产蛋白酶的菌种,为什么?
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【简答题】已知等差数列{a n }的前四项的和为60，第二项与第四项的和为34，等比数列{b n }的前四项的和为120，第二项与第四项的和为90， (Ⅰ)求数列{a n }，{b n }的通项公式； (Ⅱ)设 ，则数列{c n }中的每一项是否都是数列{a n }中的项，给出你的结论，并说明理由．
【单选题】两个正弦量为i1=20sin(628t-30°)A, i2=40sin(628t-60°)A,则( )
A.
i1比i2超前90°
B.
i1比i2滞后30°
C.
i1比i2超前30°
D.
不能判断相位关系
【单选题】两个正弦量为i1=20sin(628t-30o)A,i2=40sin(628t-60o)A,则( )。
A.
i1比i2超前90º
B.
i1比i2滞后30º
C.
i1比i2超前30º
D.
不能判断相位关系
【简答题】我国规定的安全色为____、__、__和___四种。对比色为___和___两种。
【单选题】An asset created by prepayment of an expense is:
A.
Recorded as a debit to an unearned revenue account.
B.
Recorded as a credit to a prepaid expense account.
C.
Recorded as a credit to an unearned revenue account.
D.
Recorded as a debit to a prepaid expense account.
E.
Not recorded in the accounting records until the earnings process is complete.
【单选题】An asset created by prepayment of an expense is____________.
A.
recorded as a debit to an unearned revenue account
B.
recorded as a debit to a prepaid expense account
C.
recorded as a credit to an unearned revenue account
D.
recorded as a credit to a prepaid expense account
E.
not recorded in the accounting records until the earnings process is complete
【简答题】如图，分别以四边形ABCD的四个顶点为圆心，以3为半径画弧，则图中四个阴影部分面积和为______．
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