[b]个人意见，仅供参考啊！
a) Invest $50,000 to open practice.
Dr:  long-tern asset investment    50000
   Cr:  cash                   50000
b) Bought inventory on credit $1,000
  Dr:  inventory   1000
     Cr: accounts payable   1000
c ) Bought supplies for cash $500
      Dr:  supplies equipment 500
         Cr: cash           500
D )Received cash $1,500 for providing cleaning service.
   Dr :  cash     1500
     Cr: service revenue   1500
e) Sold inventory on account $800.
  Dr; account receivable 800
      Cr: sales revenue    800
f) Paid $600 insurance premium for one year’s insurance in advance
   Dr:   prepaid   insurance 600
      Cr: cash      600
g) Recorded monthly payrol amounted to $2,500, which will be paid on Feb. 5th.
  Dr: monthly payroll expense 2500   （应该是一笔费用的 就是不知道payrol是什么意思）
    Cr: accounts payable    2500
h) At the end of Jan, recorded the insurance premimum expired in this month.
   Dr: insurance expense 600/12    50
      Cr: prepaid  insurance      50
i) Recorded the office depreciation cost for this month $300
   Dr: depreciation expense   300
      Cr: accumulate depreciation   300
j) The expected uncollected accounts amounted to $150
Dr:  bad debt expense                150
     Cr: allowance for doubtful accounts   150

感谢了。。。。