Which of the following plants produce chasmogamous and cleistogamous…

The correct answer is Option (2) → B, C and D only

Some plants produce two kinds of flowers. Chasmogamous flowers open and expose the anthers and stigma. Cleistogamous flowers never open, and pollination happens inside the closed flower.

(A) Zostera — Incorrect. This is a water plant pollinated by water. It is not an example of the two flower types.

(B) Viola — Correct. The common pansy bears both types of flowers.

(C) Oxalis — Correct. It also bears both types.

(D) Commelina — Correct. It bears both types as well.

NCERT Extract:
Pollination – “… Some plants such as Viola (common pansy), Oxalis, and Commelina produce two types of flowers – chasmogamous flowers which are similar to flowers of other species with exposed anthers and stigma, and cleistogamous flowers which do not open at all (Figure 1.9c).”