This question was rather confusingly worded. Wikipedia lists about 150 different types of rock; did it mean one of these? Or did it mean one of the three main types (sedimentary, igneous and metamorphic)?
If your mind went immediately to the 150 types, you'd have very little chance of coming back to the three within 15 seconds.
The inclusion of the words 'three main types of rock' would have been helpful.
© Macclesfield Quiz League 2022