The correct answer is - Suez Canal.
In order for the British ships to be able to reach the Far East, they needed to sail around Africa, than through the Indian Ocean and finally reach the Far East in order to be able to trade with the countries there. After the Suez Canal was made, that all changed. Instead of having to sail around Africa, the British ships were now able to just go through the Mediterranean, and through he Suez Canal to directly connect with the Red Sea and the Indian Ocean. That meant three months less in sailing, much lower expenses, and lower risk of something happening to the ship, as well as increase in the trade considering that the goods were getting on the market much quicker.
The Supreme Court case United States vs. Nixon led to limits to executive privilege.
It wasn't gaining executive privilege because Nixon was going to be impeached, but he resigned before he was removed.
He didn't get to keep the tapes private.
He didn't have a chance to lose his re-election, he resigned.
Hope this helps.
I think that your answer would be C. Private ownership, but i'm not 100% sure