Emily writes down the largest two-digit prime such that each of its digits is prime.  Krish writes down the smallest two-digit prime such that each of its digits is prime.  Kirsten subtracts Krish\textquotesingle s number from Emily\textquotesingle s number.  What answer does Kirsten obtain? ． 
选项为:A:$$14 $$  B:$$20 $$  C:$$36 $$  D:$$45 $$  E:$$50$$  请回答其中一个选项.