MCAT Question of the Day 181– Biology A radioactive dye is detected only in the cells of placental villi. Weeks earlier, it must have been injected into the: inner cell mass.trophoblastendometriumzygoteVote to see resultsVote By admin| 2015-12-29T09:16:27+00:00 January 23rd, 2016|Comments Off on MCAT Question of the Day 181– Biology Share This Story, Choose Your Platform! FacebookTwitterGoogle+Email