From those given options , option B and C we can eliminate first as in both cases the third statement is NOT a conclusion drawn from the preceding two statements.
Now coming to option D, No grape is tasteless -> Grapes are not sour --- all sour things are tasteless , here 3 rd statement is not a conclusion from precedig two statements. 2nd statement should be conclusion , not the 3rd statement as in this case.
For option A,
All sour things are tasteless ---> No grape is tasteless ---> so it is clear that Grapes are not sour. here 3rd statement is a conclusion from preceding 2 statements .
Hence, correct option is option A .