The world's most problematic aquatic weed is:

The correct answer is Option (2) → Eichhornia crassipes

Option (2) Eichhornia crassipes — Correct. Water hyacinth.

Note 1: A similar question was also asked in CUET (UG) 2023 on 22-06-2023 (Slot 3) and on 13-06-2023 (Slot 3).

Note 2: This question is from Chapter 16, Environmental Issues, of the pre-rationalised NCERT book. This chapter is not in the present NCERT book (2026-27). The extract below is from the pre-rationalised edition.

NCERT Extract (Pre-rationalised edition, Chapter 16, Environmental Issues):
Domestic Sewage and Industrial Effluents – “… You may have seen the beautiful mauve-colored flowers found on very appealingly-shaped floating plants in water bodies. These plants which were introduced into India for their lovely flowers have caused havoc by their excessive growth by causing blocks in our waterways. They grow faster than our ability to remove them. These are plants of water hyacinth (Eichhornia crassipes), the world’s most problematic aquatic weed, also called ‘Terror of Bengal’.”