【单选题】In the calculation of stability, the critical pressure P cr of a column is obtained by using the Euler’s formula, and the column is intermediate column, then ___.
A.
the real critical pressure is equal to P cr
B.
the real critical pressure is greater than P cr and shall be safe
C.
the real critical pressure is greater than P cr and shall be unsafe
D.
the real critical pressure is less than P cr and shall be unsafe