The question described how six people are standing in a row. From the statements, we know C, D, and E are together, and A and B are also together, but A is fourth from P(i.e. it is mistakenly typed instead of F. F should have been the right option as there are only A to F persons). So, the arrangement should be like this: F - C/D - E - D/C - B - A . This arranges all six people while adhering to the named restrictions. Therefore, option 3, B and F, are on the extremes.

Option 1 is incorrect because A is not on an extreme. Option 2 is incorrect because B is on an extreme but not D. Option 4, none of the above, is incorrect because there is a correct answer within the given options.