What are the features of columns?（ ） A: Columns are usually characterized by fixed names and locations. B: Columns are printed pages where manuscripts of certain contents are published. C: Columns are relatively independent in the overall layout of newspapers and periodicals. D: Articles in columns are of various styles.

If a is known to be a 2×3 matrix, then after executing a=a(:), ( ). A: a transforms to a column vector B: a transforms to 3 rows and 2 columns C: a transforms to 3 rows and 3 columns D: a transforms to 2 rows 3 and columns

Which of the following are the types of columns encountered in gas chromatography?(1) flat plates (2) packed columns (3) plastic strips (4) open tubular, or capillary columns A: 1,2 B: 3, 4 C: 1, 3 D: 2,4

The Greek orders of columns are used including

The product of two matrices ,AB is defined. Then each column of AB is a linear combination of the columns of B using weights from the corresponding columns of A.

If it is known that A is a 3×5 matrix, after executing A(:,1:2:3)=[], ( ). A: A becomes row vector B: A becomes 3 rows and 3 columns C: A becomes 3 rows and 2 columns D: A becomes 2 rows and 3 columns

下列MySQL命令正确的是( ) A: show databases; B: show tables; C: show columns; D: show columns from customers;

下列正确的命令是（ ） A: show tables; B: show columns; C: show columns from 表名; D: show databases;

Which of the following is a steel structure building? (There is only one correct answer to this question) A: The building, beams and columns are reinforced concrete, the roof and walls are profiled steel plate B: The building, beams and columns are hot rolled steel, walls are masonry block C: The building, beams and columns are timber, walls are masonry block D: The building, beams and columns are bamboo, walls are masonry block

The new type of advertisement in the classified columns of newspapers ________.