So this third carbon, this is the hydroxyl, the oxygen of that hydroxyl is connected to the hydroxyl group on the fifth carbon of the adjacent sugar. So this carbon here, this is the oxygen of that hydroxyl group and they're connected by this phosphate group. And that's exactly what we mean by three prime to five prime phosphodi as the linkage. Now, this entire chain, as we can see, basically consists of these repeating units that are composed of a phosphate group and a sugar. So we have phosphate sugar, phosphate sugar, phosphate sugar. And this continues until that nucleic acid ends.