DENDROLOGY

Detailed explanation-1: -The Brassica flower can be cut into two equal halves from any plane. So it shows radial symmetry. These flowers are referred to as actinomorphic flowers. The other flowers given can be cut into two equal halves in only one plane (bilateral symmetry ), so they are called zygomorphic flowers.

Detailed explanation-2: -In Brassica petals are in radial symmetry, i.e., all the petals are identical in size and shape. The bilaterally symmetrical flowers that can be cut into two equal halves through a single vertical plane only are said to be irregular or zygomorphic. All other given flowers are zygomorphic.

Detailed explanation-3: -For example, pies, snowflakes, and starfish are radially symmetric because they have many different lines of symmetry (dividing them into matching halves) and the lines cross one another at the center.