In which of the following groups, are all plants monoecious ?

The correct answer is Option (3)- Maize, Cucumber, Fig and Melon

The monoecious group is: Maize, Cucumber, Fig and Melon

Here's why the other options are incorrect:

• Papaya, Poplar, Rose and Fig: Papaya is dioecious (separate male and female plants).
• Cucumber, Papaya, Poplar and Rose: Same issue with Papaya being dioecious.
• Maize, Papaya, Poplar and Rose: Maize, Cucumber, and Fig are monoecious, but Rose is dioecious.

Therefore, only the group with maize, cucumber, fig, and melon consists entirely of monoecious plants.