In how many ways can 11 books on English and 9 books on French be placed in a row on a shelf so that two books on French may not be together?	Pick one:  A) 220 .  B) 240  C) 260  D) 280  E) 300

Rationale: we have 11 english and 9 french books , no french books should be adjacent . imagine 11 english books in a row and empty slots like below : * e * e * e * e * e * e * e * e * e * e * e * now if 9 french books would be placed in 12 empty slots , all french books will be separated by english books . so we can ` ` choose ' ' 9 empty slots from 12 available for french books , which is 12 c 9 = 220 . ans : a _________________
Answer: A