RDD entry

Provision for doubtful debts is Rs.1000 &

debtors are Rs.90,000 at end of year,

provision for doubtful debt 1% required, then

the entry 

a) P & L A/c  Dr  900   

  To provision for doubtful debts 900

b) Provision for doubtful debts 900

  To P & C A/c     900

c) P & L A/c  Dr  100    

   To RDD A/c  100

d) none of these

what is the answer n reason for the same????????