The primary xylem in roots is: MCQ with Answer and Explanation

Explanation:
Thyroxine (T4) and Triiodothyronine (T3) are the main hormones secreted by the thyroid gland. They play a crucial role in regulating the basal metabolic rate (BMR), which is the rate at which the body uses energy at rest. They also influence growth, development, and body temperature. Calcitonin, also from the thyroid, regulates blood calcium.

Explanation:
Adenine (A) pairs with thymine (T) via two hydrogen bonds. Guanine (G) pairs with cytosine (C) via three hydrogen bonds. This base pairing (complementarity) is key to the double helix structure and ensures accurate replication and transcription. The higher number of bonds between G-C contributes to DNA stability; GC-rich regions are harder to denature.

Explanation:
Bacteria are prokaryotes that primarily reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Fungi are eukaryotes characterized by having cell walls primarily composed of chitin, a tough polysaccharide. Viruses lack cellular structure and metabolic machinery; they are obligate parasites that rely entirely on the host cell's machinery for replication. Thus, statements 1 and 3 are correct.