【单选题】13 Which of the following correctly describes the imprest system for operating petty cash? A A All expenditure out of petty cash must be supported by a properly authorised voucher.
B.
A regular equal amount of cash is transferred into petty cash.
C.
The exact amount of expenditure out of petty cash is reimbursed at intervals.
D.
A budget is fixed for a period which petty cash expenditure must not exceed.
【简答题】某研究小组对用H 2 O 2 分解生成H 2 O和O 2 的实验条件进行探究.他们进行了以下实验: ①往盛有5mL 5% H 2 O 2 溶液的试管中,伸入带火星的木条,木条不复燃. ②往盛有5mL w% H 2 O 2 溶液的试管中,加入a g MnO 2 ,伸入带火星的木条,木条复燃. ③往盛有5mL w% H 2 O 2 溶液的试管中,加入a g Fe 2 O 3 ,伸入带火星的木条,木条复...