Which phenomenon is responsible for the reddish appearance of the Sun at sunset?

The correct answer is B: Scattering of light. At sunset, light travels through a longer path in the atmosphere. Shorter wavelengths (blue) scatter more (Rayleigh scattering), leaving longer wavelengths (red) to reach the observer.

The double fertilization process unique to angiosperms results in the formation of:

The correct answer is A: Embryo and endosperm. One sperm nucleus fertilizes the egg (embryo), another fuses with polar nuclei (endosperm); this endosperm provides nutritive tissue for the developing embryo.

Which organelle is responsible for the synthesis of ribosomal RNA in plant cells?

The correct answer is B: Nucleolus. The nucleolus within the nucleus is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly in eukaryotic cells.