Hint: A convex lens works very similar to a concave mirror so if the student knows what a concave mirror does with the light rays, he\she can easily guess the answer.Complete step by step answer:
A convex lens is thick in the middle and gets thinner towards the edges. When parallel light rays are incident on a convex lens, they get focussed to a focal point after refraction through the lens. Since the refracted rays converge to the focus after refraction a convex lens is also known as a converging lens.
The correct answer is B. Converging lensAdditional information:
The properties of images formed by a convex lens vary with distance of the object from the lens.
If the object is at an infinite distance its image would be Diminished, Real and inverted. If the object is going closer to the lens its image is real and inverted but it gets magnified as the object approaches the focus. When the object is at focus its image is real, enlarged and is formed at infinity. If the object is between the focus and the lens the image becomes virtual, magnified and erect and on the same side as the lens.
Note: Both convex lens and concave mirror converge the light rays to a focus after refraction/reflection and they both have their focal length positive.