The scientist who discovered the concept of 'natural killer' cells was: MCQ with Answer and Explanation

Explanation:
The nucleolus is a prominent, non-membrane-bound structure within the nucleus. It is the site of active ribosomal RNA (rRNA) synthesis and the assembly of ribosomal subunits. These subunits then exit the nucleus through nuclear pores to combine in the cytoplasm and form functional ribosomes for protein synthesis.

Explanation:
Rickets is a childhood bone disorder caused by a severe deficiency of Vitamin D (Calciferol), or sometimes calcium or phosphate. Vitamin D is essential for the absorption of calcium and phosphorus from the gut. Its deficiency leads to soft, weak bones, resulting in skeletal deformities like bowed legs, delayed growth, and bone pain. Osteomalacia is the adult equivalent.

Explanation:
The carpel is the female reproductive organ of a flower, consisting of the ovary, style, and stigma; the stigma is the terminal, sticky receptive surface where pollen grains land and germinate. The stamen is the male reproductive organ, consisting of the filament and the anther; the anther is the terminal sac where pollen grains (male gametophytes) are produced. After fertilization, the ovule develops into the seed, while the ovary wall matures and develops into the fruit. Thus, statements 1 and 2 are correct.