Answer:
D. vasectomy
Step-by-step explanation:
Although it could be reversed, a vasectomy is generally considered a permanent method of birth control, and it's very safe long term, with very little risk of failing.
A. Condom: is not a permanent method of birth control, as you have to remind to use it every time... and the condom itself might fail (burst, slip, and so on)
B. Outercourse: even if the guy pulls out before total ejaculation, some drops may have leaked before the exit and cause a pregnancy.
C. Implant, it's usually a temporary implement and it has to be renewed or changed after a certain period of time.