A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic division occurs after the formation of zygote. The adult filament of this alga has

1. haploid vegetative cells and diploid gametangia

2. diploid vegetative cells and diploid gametangia

3. diploid vegetative cells and haploid gametangia

4. haploid vegetative cells and haploid gametangia

(d)
A multicellular gametophyte (gametangia), which is haploid (n) alternates with a multicellular sporophyte, which is diploid (2n). A mature sporophyte produces spores (haploid cells) by meiosis, a process which reduces the number of chromosomes to half, from 2n to n.