Answer:
second / fourth options
Explanation:
A linear function has both x and y to the power of 1
y = x² - 19 ( x raised to power 2 ) ← not linear
x = y ( both variables are raised to power of 1 ) ← linear
y = 3x² ( x raised to power of 2 ) ← not linear
x = 2y + 4 ( both variables raised to power of 1 ) ← linear
y = x(2x + 4), that is
y = 2x² + 4x ( one term has variable raised to power 2 , that is x² ) ← not linear