Which discovery did scientists make at mid-ocean ridges that caused them to conclude that new rock was being formed by molten material?

magnetic banding

pillow-shaped rocks

older rocks farther from the ridge

rocks with similar characteristics

Older rocks farther from the ridge.

Answer: Option (C)

Explanation: It is because as we move away from the Mid-Oceanic Ridge (MOR), we observe the older rocks. And along the MOR, new rocks are being generated due to instant cooling of the sea water, whereas pillow basalts only tells us about the rocks formed due to cooling of sea water but it wont differentiate either the rock is young or old.

Thus the scientists lead into the discovery of new rocks at the MOR formed by molten materials.

Hence, the correct answer is option (C)