This question is incomplete because the options are not given; here is the complete question:
Which phrase describes a sill?
A. Fills in valleys and rivers
B. Is a hardened magma intrusion
C. Cuts vertically through older rock layers
D. Is built up by numerous eruptions over thousands of years
The correct answer is B. Is a hardened magma intrusion
Explanation:
Sills are horizontal layers in the soil that form as a result of magma. Also, sills are considered sheet intrusion because the hardened magma gets into older rock layers or soil layers and cuts the rocks horizontally. Moreover, the type of intrusion is studied by geologists to understand the formation and age of soil layers and this differs from other intrusions due to its composition and horizontal formation. According to this, the correct answer is B.
