To solve this problem, we need to interpret the given floral formula and identify the corresponding plant.$\\$The floral formula provided is:$\\ \oplus \; ♀ \; K_{(5)} \; C_{(5)} \; A_{5} \; G_{(2)}^{\underline{\smash{i}}} \\$Let's break down each component:$\\ \oplus :$The flower is actinomorphic (radially symmetrical).$\\ ♀ :$The flower is bisexual, containing both male and female reproductive organs.$\\ K_{(5)} :$There are 5 sepals, which are fused (calyx).$\\cC_{(5)} :$There are 5 petals, which are fused (corolla).$\\ A_{5} :$There are 5 stamens (androecium).$\\ G_{(2)}^{\underline{\smash{i}}} :$There is a bicarpellary (2 carpels) gynoecium, which is inferior (indicated by the line under the 'G').$\\$Now, let's match this floral formula with the given options:$\\$1. Allium: Typically has a different floral structure.$\\$2. Sesbania: Typically has a different floral structure.$\\$3. Petunia: Matches the given floral formula. Petunia flowers are actinomorphic, bisexual, with fused sepals and petals, 5 stamens, and a bicarpellary inferior ovary.$\\$4. Brassica: Typically has a different floral structure.$\\ \textbf{Therefore, the correct option is Option 3: Petunia.}$