According to Newton's second law of motion, the acceleration of a body is directly proportional to the net force applied to it, and it is given by the formula:
\[ a = \frac{F}{m} \]
where \( a \) is the acceleration, \( F \) is the net force, and \( m \) is the mass of the body.
In the first trial, a net force of 0.7 N results in a certain acceleration. If in the second trial half of that force is applied (which is 0.35 N), the acceleration will also be half of the original acceleration because the force is halved (assuming the mass of the body remains constant).
Thus, the correct response is:
The acceleration is half of its original value.