After so many trials, the experiment __________

Analyze the question The sentence "After so many trials, the experiment __" needs a phrasal verb that means the experiment finally succeeded after repeated effort.

Explain the concept "Pay" combines with different particles to form phrasal verbs with different meanings:

• pay up: to give the money owed, often reluctantly (e.g., "Pay up your debt!")
• pay for: to give money in exchange for something, or to suffer for a wrong (e.g., "He will pay for his crimes.")
• pay out: to spend or hand over a large sum of money (e.g., "The insurance company paid out millions.")
• pay off: to bring a good result or success after effort or risk (e.g., "Her hard work paid off.")

Show the solution

1. The sentence talks about "many trials", meaning repeated attempts and effort.
2. The experiment has no money to hand over, so "paid up" and "paid out" do not fit.
3. "Paid for" would need an object (paid for what?), and it doesn't convey success.
4. "Paid off" means the effort finally produced a good result, which fits perfectly.

Complete sentence: After so many trials, the experiment paid off.

Correct answer: D (paid off)

Exam tip When you see "after so many attempts/efforts/trials" followed by a blank, think "paid off". It is the standard phrase for "effort that finally brings success". Remember: pay off = payoff = reward for effort.