chemistry help

The experiment was repeated at 20 °C using a 250 cm3 conical flask.

Which statement is correct about the time taken for the cross to disappear when using the larger conical flask?

The time taken will be increased by using the larger conical flask.

Why is this the correct answer?

I think in this experiment you are really measuring the time it takes for enough precipitate to form to create a thick enough layer in the conical flask so that the cross is covered. If you use a larger conical flask, the same mass of precipitate is more spread out so more is needed to form a thick enough layer which takes more time.