The power that has been deemed “necessary and proper” typically refers to the powers interpreted under the Necessary and Proper Clause (also known as the Elastic Clause) of the U.S. Constitution. This clause allows Congress to create laws that are deemed necessary and proper to carry out its enumerated powers.
Among the options provided, the power to institute a draft is an example of a power that could be considered "necessary and proper" as it relates to Congress's power to raise and support armies.
Therefore, the answer is: the power to institute a draft.