In multicellular organisms, life begins as a single cell until blank occurs

In multicellular organisms, life begins as a single cell until fertilization occurs.

Explanation:

In a multicellular organism, the gametes, that is haploid (single-celled n) eggs (female) and sperm cells (male) are fused by fertilization to form the zygote (2n). The zygote then undergoes several cycles of divisions to become an embryo and then foetus. After gestation, a full multicellular organism is formed.

All multicellular organism are started from single cells or germ cells from each parent.