In the common type of bi-focal lenses, the upper and lower portions have different characteristics to provide clear vision for both near and distance vision. Option 1 states that the upper portion is concave, while the lower portion is convex. A concave lens is thinner at the center and thicker at the edges, causing light rays to diverge. This type of lens is used for correcting nearsightedness. On the other hand, a convex lens is thicker at the center and thinner at the edges, causing light rays to converge. This type of lens is used for correcting farsightedness.

Option 2, which states that the upper portion is convex and the lower portion is concave, is not correct as it reverses the typical configuration of bi-focal lenses. The upper portion should be concave to correct nearsightedness, while the lower portion should be convex to correct farsightedness.

Option 3 and option 4, which suggest that both the upper and lower portions are either concave or convex, are also incorrect. Bi-focal lenses are designed to correct different types of vision problems simultaneously, and for that reason, they have different characteristics in the upper and lower portions.

Therefore, the correct answer is option 1, where the