For a closer look when shaving: a plane mirror is used. a concave mirror is used. a convex mirror is used.

Plane mirror always forms an image of same size as that of object

Concave mirror can form a virtual image that is greater than the size of object

convex mirror will always form a virtual image that is smaller in size

So overall for closer look during shaving in mirror we need a mirror that will form virtual image of greater size

So here correct answer would be

A concave mirror is used.

for this purpose the person should be closer to mirror as we know that image will be virtual and magnified only when the object is between focus and pole of the mirror

a straight line sloped