在常温下10mL pH＝10的KOH溶液中，加人一定量的pH＝4的一元酸HA溶液至pH刚好等于7，则对反应后溶液的叙述正确的是( )
A．c(HA)+c(A-)=10-4mol/L B．c(H＋)＝c(OH－)＜c(K＋)＜c(A－)
C．V总≤20mL D．酸和碱一定恰好中和
答案：C
如果HA为强酸，等体积恰好中和，呈中性，V总=20mL；如果为弱酸，酸的浓度远大于碱的浓度。总体积小于20ml。
| Based on the following data to answer A company had the following changes in its balance sheet accounts: An increase in accounts receivable $ 50 A decrease in accounts payable $ 40 An increase in inventory $ 60 Sale of common stock $150 Repayment of debt $ 20 Depreciation $10 Net Income $ 700 |
The company’s cash flow from operations is:（）
A. $750.
B. $ 640.
C. $560.