In which of the following plants can the flower be divided into two...

Flowers that can be divided into two equal radial halves in any radial plane passing through the centre are called actinomorphic (radially symmetrical).

Examples of actinomorphic flowers include mustard, datura, and chilli.

Flowers that can be divided into two similar halves only in one particular vertical plane are called zygomorphic (bilaterally symmetrical). Examples include pea, gulmohur, bean, and Cassia.

Flowers that cannot be divided into two similar halves by any vertical plane passing through the centre are asymmetric (irregular). An example is Canna.

Therefore, mustard has actinomorphic flowers.

Answer: Mustard