The structure that forms the physical barrier between the blood and the brain is the: MCQ with Answer and Explanation

Explanation:
Human males are XY and produce X and Y sperm; females are XX. The sperm determines sex. Thus, C is correct.

Explanation:
Bt cotton is a transgenic crop developed by inserting cry genes (e.g., cryIAc, cryIIAb) from the soil bacterium Bacillus thuringiensis (Bt). These genes code for crystal proteins (Cry proteins) that are toxic to certain insect pests, particularly the cotton bollworm. When the insect ingests the protein, it is activated in its alkaline gut, creating pores in the gut lining, leading to the insect's death.

Explanation:
Antonie van Leeuwenhoek, a Dutch tradesman, is credited as the 'father of microbiology'. In the 1670s, using his own handcrafted, high-quality single-lens microscopes (which could magnify up to 270x), he was the first person to observe and describe living, single-celled organisms, which he called 'animalcules'. These included bacteria, protozoa, and spermatozoa. Robert Hooke observed dead cells (cork) and coined the term 'cell'.