( a ) male gamete fusing with egg cell and male gamete fusing with three antipodal cells
( b ) male gamete fusing with one of the synergids and male gamete fusing with three antipodal cells
( c ) male gamete fusing with egg cell and male gamete fusing with diploid secondary nucleus
( d ) male gamete fusing with one of the synergids and male gamete fusing with two polar nuclei