Final answer:
An electron with a principal quantum number of 4 and an azimuthal quantum number of 2 is in the 4d subshell since the azimuthal quantum number corresponds to the d subshell when its value is 2.
Step-by-step explanation:
An electron moving in an orbit with a principal quantum number of 4 and an azimuthal quantum number of 2 is located in the 4d subshell. The principal quantum number corresponds to the shell number, and the azimuthal quantum number, also known as the angular momentum quantum number, corresponds to the subshell.
The subshells have designated letters (s, p, d, f) which represent increasing azimuthal quantum numbers (0, 1, 2, 3, respectively). Therefore, with a principal quantum number of 4, the possible subshells would be 4s, 4p, 4d, and 4f. Since the azimuthal quantum number given is 2, it corresponds to the d subshell, making the correct answer 4d.