Answer: A) elastic clause
Step-by-step explanation:
The powers of Congress as stated by the Constitution of the United States are limited which means that sometimes, Congress may not have the Constitutional power to carry out some duties necessary for them to fulfil some of their mandate.
This is where the Elastic Clause comes in. The Elastic clause gives Congress the flexibility it needs by allowing it to do what it must in order to carry out its duties.
President Jefferson used this clause in the Louisiana Purchase because the Constitution did not give either him or Congress the power to buy land but by using the Elastic Clause he was able to do so.