Chasmogamous flowers are -

The correct answer is Option (2) → Similar to flowers of other species with exposed anthers and stigma

A plant that bears two types of flowers has chasmogamous and cleistogamous flowers. “Chasmo” means open, and “cleisto” means closed.

Option (1) Dissimilar to flowers of other species with exposed anthers and stigma — Incorrect. Chasmogamous flowers are ordinary open flowers. They look and work like the flowers of other species, so “dissimilar” is wrong.

Option (2) Similar to flowers of other species with exposed anthers and stigma — Correct. These flowers open and expose their anthers and stigma. So pollen from other flowers can reach the stigma, and cross-pollination is possible.

Option (3) Similar to flowers of other species with fused anthers and stigma — Incorrect. The anthers and the stigma are not fused in these flowers. They are separate and exposed, so pollen can be carried between flowers.

Option (4) Flowers which do not open at all — Incorrect. This describes the cleistogamous flowers, the other type. Their anthers and stigma lie close together inside the closed flower, so they can only be self-pollinated.

NCERT Extract:
Pollination – “… (i) Autogamy : In this type, pollination is achieved within the same flower. Transfer of pollen grains from the anther to the stigma of the same flower (Figure 1.9a). In a normal flower which opens and exposes the anthers and the stigma, complete autogamy is rather rare. Autogamy in such flowers requires synchrony in pollen release and stigma receptivity and also, the anthers and the stigma should lie close to each other so that self-pollination can occur. 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).”