Question

multiple choice question
it was difficult to find evidence for the existence of a sixth quark because
○ high - speed collisions never result in the release of the sixth quark
○ only about one - billionth of a percent of collisions studied showed its presence
○ scientists needed to come up with a completely different method to detect it

Explanation:

Quarks are sub - atomic particles. The difficulty in finding evidence for the sixth quark was due to its extremely low occurrence rate in collisions. Only a minuscule fraction (about one - billionth of a percent) of the studied collisions showed its presence, making detection challenging.

Answer:

Only about one - billionth of a percent of collisions studied showed its presence