Which feature is considered a natural barrier? (1) great rift valley (2) aswan dam (3) panama canal (4) great wall of china

Gemstones are commonly found in pegmatites, which are igneous rocks that are a. exceptionally mafic b. exceptionally coarse grained c. exceptionally fine grained d. extrusive, forming from lava

Given f(x) = 3x= 1 and g(x) = 2x-3, for which value of x does g(x)= f(2)? its for algebra

The magnitude of an earthquake is typically calculated according to the scale.           a. mercalli   b. fujita   c. richter   d. saffir-simpson