From 1990 to 2001, German currency included coins called $pfennigs$, worth 1 pfennig each, and $groschen$, worth 10 pfennigs each. Which equation represents the number of pfennig coins, $p$, and groschen coins, $g$, that have a combined value of $85$ pfennigs? 
选项为:A:$p+g=85$  B:$p+10g=85$  C:$10p+g=85$  D:$10(p+g)=85$  请回答其中一个选项.