Eukaryotic sexual life cycles show tremendous variation. of the following elements, which do all sexual life cycles have in common? i. alternation of generations ii. meiosis iii. fertilization iv. gametes v. spores

II. meiosis

III. fertilization

IV. gametes

Explanation:

Gamete formation and fertilization are the processes performed by all the sexually reproducing organisms. Gametes are the cells that are formed in the male and female sexual organs of these organisms. Formation of gametes occurs by meiosis and therefore, the gametes of a diploid organism are always haploid.

Male and female gametes fuse during the process of fertilization and form the zygote which in turn divide repeatedly to produce an embryo. For instance, sperms and eggs are the male and female gametes that are formed in testes and ovaries of male and female human individuals respectively. The fusion of sperm and egg produces a zygote that finally develops into a young one.  

b tumor cells have a cell wall instead of a membrane

explanation:

tumor cells different from normal cells because tumor cells have a cell wall instead of a membrane.