The second option is correct: 1/2 being split evenly into two groups.
It can help to read it out loud: “One half divided BY two.”
It’s basically halving the 1/2, which would make it 1/4. Splitting the fraction in half.
For the first option to be true, the equation would have to be 2 ÷ 4 = 1/2. But it’s not, so that option is incorrect.