Given a scientific passage and an answer, generate a question for the given answer.

[EX Q]: Passage: Electrons are always added to the lowest energy level first until it has the maximum number of electrons possible, and then electrons are added to the next higher energy level until that level is full, and so on. The maximum number of electrons at a given energy level depends on its number of orbitals. There are at most two electrons per orbital. Answer: the lowest
[EX A]: Electrons are always added to which energy level first?

[EX Q]: Passage: Test wells are drilled to monitor groundwater pollution. Answer: test wells
[EX A]: What are drilled to monitor groundwater pollution?

[EX Q]: Passage: Surface currents are like streams flowing through the surface of the ocean. They are caused mainly by winds. Earth's rotation influences their direction. This is called the Coriolis effect. Surface currents may affect the climate of nearby coasts. Answer: winds
[EX A]:
What are surface currents mainly caused by?