In Begum Rokeya Sakhawat’s book ”Sultana’s Dream” we find the following excerpt, ”Where are the men?...where they ought to be...we shut our men indoors...just as we are kept in the zenana?” What do these lines describe?

The correct option is Reversal of roles of Gender.

Begum Rokeya Sakhawat Hossain’s famous feminist utopian story "Sultana’s Dream," written in 1905, depicts a fictional society called "Ladyland" where traditional gender roles are completely inverted.
In this state, women manage all external affairs, governance, and scientific pursuits, while men are relegated to domestic spaces.

The excerpt "Where are the men?...where they ought to be...we shut our men indoors...just as we are kept in the zenana?" directly refers to this structural inversion.
The "zenana" refers to the traditional outer/inner quarters where women were historically secluded under the purdah system. By shutting men indoors in the same manner, the author illustrates a literal reversal of gender roles to critique the patriarchal restrictions imposed on women in her contemporary society.