Sentence Correction

Bottle-nosed dolphins have a highly developed sense of taste , enabling them to detect various chemicals in the water , However, since this animal has no olfactory lobe, they apperently have no sense of smell.

A. since this animal has
B. these animals have
C. those animals have
D.Since these animals have
E. Since the dolphin are

I am confused in the POE for B and D.
I Though 'However' is counter and 'Since' causes redundency when used with however so selected the B.

Please advise.

OA D