Regarding Assertion (A) and its Reason (R) :- <br> A: Fishes, amphibians, reptiles, birds are placed in Phylum Chordata but not mammals . <br> R: They are placed in a single phylum based on the common features like presence of notochord and dorsal hollow neural system

Question

( a ) A is incorrect but R is correct
( b ) Both A and R are correct but R is not the correct explanation for A
( c ) A is incorrect but R is correct; R is the correct explanation for A
( d ) A is correct but R is incorrect