To solve this problem, we need to identify who experimentally verified the chromosomal theory of inheritance. Let's analyze the options:$\newline \bullet$Sutton:$\newline$ - Walter Sutton, along with Theodor Boveri, proposed the chromosomal theory of inheritance, which states that genes are located on chromosomes.$\newline$ - However, Sutton did not perform experimental verification of this theory.$\newline \bullet$Boveri:$\newline$ - Theodor Boveri contributed to the chromosomal theory by studying sea urchins, but he did not provide experimental verification of the theory.$\newline \bullet$Morgan:$\newline$ - Thomas Hunt Morgan is credited with the experimental verification of the chromosomal theory of inheritance.$\newline$ - He conducted experiments on fruit flies (Drosophila melanogaster) and demonstrated that genes are linked on chromosomes.$\newline$ - His work provided concrete evidence supporting the chromosomal theory.$\newline \bullet$Mendel:$\newline$ - Gregor Mendel is known for his foundational work on the laws of inheritance using pea plants.$\newline$ - Mendel's work laid the groundwork for genetics, but he did not work on the chromosomal theory.$\newline$Therefore, the correct answer is Option 3: Morgan, who experimentally verified the chromosomal theory of inheritance.