No matter how far you stand from a mirror your image appears erect. The mirror is likely to be

(a) concave mirror (b) convex lens (c) concave lens (d) convex mirror

(d) When an object is placed between the pole and principal focus of a concave mirror, the image formed is virtual, erect, and larger than the object.

(d) A convex mirror always gives a virtual and erect image of smaller size of the object placed in front of it. Similarly, a plane mirror will always give a...

(b) virtual, behind the mirror and of the same size as the object.

Concave mirror can give an erect and enlarged image of an object, when object is placed between pole and focus of the mirror.

The image formed by a concave mirror is virtual, erect and larger only when the object is placed between the pole of the mirror and its principal focus. So correct...

(b) concave lens provided the image is smaller than object. 

(iii) 6 m Explanation: As David moves 1 m towards the mirror, the image also moves 1 m towards the mirror. Now the distance between David and mirror is 3 m and...

(c) the object is real but the image is virtual (d) the object is virtual but the image is real.

I walked about 7-8 kilometres at one time and I think I can walk as far as up to 15 kilometres at a time.