The correct option is C 1:√3:2
Let the angles of the triangle be x, 2x and 3x.
Then, x+2x+3x=360°.
So, the angles are 30°, 60° and 90°.
Let a, b and c be the sides opposite to these angles.
Then,
asin A=bsin B=csin C⇒a:b:c=sin 30°:sin 60°:sin 90°⇒a:b:c=12:√32:1=1:√3:2