题目内容

对于承受静力荷载和间接承受动力荷载的组合梁,坚决不允许腹板在梁整体失稳之前屈曲。

A. 对
B. 错

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横向荷载的临界值仅与它自身大小有关,而与沿梁高的作用位置无关。

A. 对
B. 错

梁的整体失稳现象是指

Heteroskedasticity means that

A. homogeneity cannot be assumed automatically for the model.
B. the variance of the error term is not constant.
C. the observed units have different preferences.
D. agents are not all rational.

With heteroskedastic errors, the weighted least squares estimator is BLUE. You should use OLS with heteroskedasticity-robust standard errors because

A. this method is simpler.
B. the exact form of the conditional variance is rarely known.
C. the Gauss-Markov theorem holds.
D. your spreadsheet program does not have a command for weighted least squares.

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