Which organelle is known as the 'powerhouse of the cell'? MCQ with Answer and Explanation

Explanation:
Retroviruses (e.g., HIV) possess two copies of single-stranded RNA and the enzyme reverse transcriptase, which transcribes the RNA into DNA upon infection. This DNA integrates into the host genome. Other viruses may have dsDNA, ssDNA, or dsRNA, but the defining feature of retroviruses is the RNA genome and reverse transcription.

Explanation:
The inner surface of the small intestine is lined with finger-like projections called villi, which increase the surface area for absorption. The epithelial cells (enterocytes) covering these villi have their own microscopic, finger-like projections on their apical surface, called microvilli. Collectively, these microvilli form a 'brush border'. This further massively increases the surface area, maximizing the efficiency of nutrient absorption. Cilia are motile, and stereocilia are found in the inner ear and epididymis.

Explanation:
Vascular cryptogams are plants that possess vascular tissues (xylem and phloem) but reproduce via spores rather than seeds. Pteridophytes, such as Selaginella (spike moss), ferns, and Equisetum, fit this description. Funaria and Marchantia are bryophytes (non-vascular cryptogams), and Pinus is a gymnosperm (a vascular phanerogam or seed-producing plant).