The element present in the center of the chlorophyll molecule is: MCQ with Answer and Explanation

Explanation:
Lymphatic vessels collect interstitial fluid (lymph) and return it to the venous circulation (subclavian veins). This maintains fluid balance. Along the way, lymph nodes filter pathogens. The heart pumps blood, kidneys filter blood, lungs exchange gases. The lymphatic system is unidirectional.

Explanation:
Type 1 diabetes mellitus is an autoimmune disease where beta cells of the pancreas are destroyed, leading to little or no insulin production. Patients require insulin injections. Type 2 involves insulin resistance. Diabetes insipidus involves ADH deficiency, Cushing's syndrome is cortisol excess.

Explanation:
Mendel selected Pisum sativum because it had distinct contrasting traits, was easy to cultivate, and was naturally self-pollinating, allowing controlled crosses. R explains A correctly.