An object is initially placed 40cm in front of a thin convex lens of focal length 20cm and is then moved slowly to a position 5cm from the lens. Which statement best describes how the nature and size of the image change during this movement?
a) Remains real and inverted throughout; its size continuously increases as the object is brought closer to the lens
b) Always virtual and erect; its size steadily decreases as the object approaches the lens
c) Starts real, inverted and equal in size at 40cm; becomes larger and real as the image shifts away; at 20cm the image is at infinity; for object distances less than 20cm the image becomes virtual, erect and enlarged
d) Starts real and diminished; when the object reaches 20cm the image jumps to f instead of 2f; for still smaller object distances it stays real but becomes enlarged