Like D. Codon is the answer
Answer:
Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)
Explanation:
B
The other problems are not as easily solved; whereas, data collection over long periods of time is possible and was already done in the past, eg temperature and weather patterns. Therefore, this is the easiest limitation to overcome.
A The continents were once joined together
Explanation:
All the continents were once together making a huge one called Pangea.