绘图题：已知单列向心球轴承：D＝40mm，d＝17mm，B＝12mm，倒角为1，用简化画法画出单列向心球轴承。
参考答案：
亚硝酸(HNO2)的下列性质中，可以证明它是弱电解质的是
A．亚硝酸不稳定，易分解
B．0.1 mol·L－1的亚硝酸溶液的pH<7
C．把pH=2的亚硝酸溶液稀释100倍后pH=3.5
D．100 mL l mol·L－1的亚硝酸溶液恰好与100 mL l mol·L－1的NaOH溶液完全反应
Under IFRS, which of the following is most accurate if the outcome of a longterm contract cannot be measured reliably and it is probable that the costs will be recovered（）
A. The company reports revenue to the extent of contract costs incurred.
B. The company does not report any income until the contract is substantially finished.
C. The company estimates what percentage of the contract is complete and then reports that percentage of the total contract revenue in its income statement.
