$(14)$ The term 'buttering' is used when overlaying a steel component with a stainless steel alloy, but what does it mean?

$($a$)$ The object of the butter coat is to minimise dilution and seal the surface of the parent metal

$($b$)$ To ensure good alloying of the overlay material

$($c$)$ To ensure rapid deposition of the overlay material

$($d$)$ To ensure a smooth weld profile