润滑油“三级过滤”目的是为了及时准确的给润滑点加油。
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冬期采用普通硅酸盐水泥，有抗冻要求的混凝土不宜采用（）。
空调水系统工程应冲洗干净不含杂质，并排除管道系统中的（）
A. 杂质
B. 空气
C. 铁锈
Which four statements correctly describe functions that are available in SQL? （）
A. INSTR returns the numeric position of a named character.
B. NVL2 returns the first non-null expression in the expression list.
C. TRUNCATE rounds the column, expression, or value to n decimal places.
DECODE translates an expression after comparing it to each search value.
E. TRIM trims the heading or trailing characters (or both) from a character string.
F. NVL compares two expressions and returns null if they are equal, or the first expression if they are not equal.
G. NULLIF compares two expressions and returns null if they are equal, or the first expression if they are not equal.
生物学活性测定法测定细胞因子的共同缺点是特异性不高。（）
A. 正确
B. 错误
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