Answer: Option A
Smooth : having an even and regular surface; free from perceptible projections, lumps, or indentations.
Indifferent : having no particular interest or sympathy; unconcerned.
Gainful : serving to increase wealth or resources; providing money or other benefit.
Rough : having an uneven or irregular surface; not smooth or level.
Glib : (of words or a speaker) fluent but insincere and shallow; smooth-talking.
Synonym of Glib is Smooth