What is the setback of using the gravitational slingshot maneuver to send spacecraft to another planet?

A)
Time consuming
B)
Less economical
C)
More fuel consumption
D)
Limitation of correct alignment of planets

Correct Answer :   Limitation of correct alignment of planets


Explanation : On of the major setbacks for using the gravitational slingshot is that there are very rare occurrences for the planets to align in way expected for the optimum slingshot to occur. It can take several years, decades to achieve a perfect alignment of the celestial bodies.
On the other hand, slingshot mostly accelerates the spacecraft thus making it less time consuming. And since it makes use of lesser fuel, it is ore economical.