Final answer:
The U.S. House of Representatives can initiate taxing and spending bills, a power not held by the Senate. However, the unique action mentioned in the options, that the Senate can take and the House cannot, is d) Filibustering.
Step-by-step explanation:
The unique step that the U.S. House of Representatives can take which the Senate cannot is related to budget bills. Specifically, all taxing and spending bills must originate in the House. The Senate does hold some unique powers as well; only the Senate can approve treaties and conduct filibustering. However, proposal of amendments and ratification are actions both chambers are involved in, and are not exclusive to the House.
Therefore, the correct answer to the student's question, considering the options provided, would be d) Filibustering.
Filibustering is a tactic used in the Senate to prolong debate and delay or prevent a vote on a bill. The House does not have the ability to filibuster. Conversely, while the House is responsible for initiating bills related to revenue and budget, it cannot ratify treaties or filibuster, which are actions exclusive to the Senate.