Which mirror or lens can form a virtual, erect and highly diminished image of object?

Question 4

You are provided with a concave mirror, a convex mirror, a concave lens and a convex lens. To obtain an enlarged image of an object you can use either

(a) concave mirror or convex mirror.

(b) concave mirror or convex lens.

(c) concave mirror or concave lens.

(d) concave lens or convex lens.

Question 7

You are provided with a convex mirror, a concave mirror, a convex lens and a concave lens. You can get an inverted image from

(a) both concave lens and convex lens.

(b) both concave mirror and convex mirror.

(c) both concave mirror and convex lens.

(d) Both convex mirror and concave lens.

Which of the following can make a parallel beam (a) concave mirror as well as concave lens (b) convex mirror as well as convex lens (c) concave mirror as well as convex lens (d) convex mirror as well as concave lens

Why focal length of convex mirror and convex lens is positive while concave mirror and concave lens negative?