If the net external force on a body is zero, its acceleration:
• A
must be equal to zero
• B
may be equal to zero
• C
must be non-zero
• D
must be equal to $g$

Solution

Newton's 2nd law states that force on a body is equal to mass times acceleration. For a zero external force, there will be a zero acceleration for body. Hence, acceleration will be zero for no net external force.