What was unknown to scientists during Wegner's time?
A. The coasts of some continents fit together.
B. Earth's crust is made of plates that move.
C. Fossils were found in many places.
D. Mountain ranges of some continents lines up.
B. Earth's crust is made of plates that move.
During Wegener's time, the concept of Earth's crust being made of plates that move (option B) was unknown to scientists.
During Wegener's time, which refers to the early 20th century, the concept of Earth's crust being made of moving tectonic plates (option B) was unknown to scientists. Alfred Wegener, a German scientist and meteorologist, proposed the theory of continental drift, which suggested that the continents were once joined together in a single landmass called Pangaea. However, at that time, the notion that the Earth's crust is divided into separate plates that are in constant motion was not yet understood.
The other options mentioned in the question were actually observations that were known to scientists during Wegener's time. The idea that the coasts of some continents fit together (option A) was a key observation supporting continental drift. Wegener noticed the remarkable match between the east coast of South America and the west coast of Africa. Similarly, the evidence of fossils found in different continents (option C) further suggested that the continents were once connected. Finally, the alignment of mountain ranges in some continents (option D), such as the Appalachian Mountains in eastern North America and the Caledonian Mountains in Europe, also provided evidence for the theory of continental drift.
Therefore, the correct answer is option B: Earth's crust is made of plates that move, as this understanding came after Wegener's time.