Option 1 states that a combination of a point source and an opaque screen would produce the sharpest shadow of an opaque object. A point source refers to a light source that emits light from a single point, such as a small light bulb or a laser. An opaque screen, on the other hand, prevents light from passing through it, creating a solid barrier.

Option 2 suggests an extended source, which refers to a light source that emits light from a larger surface area, such as a fluorescent tube or a window. However, this is not the best combination for producing a sharp shadow because an extended source would result in a larger, less defined shadow.

Option 3 mentions a combination of a point source and a transparent screen. A transparent screen allows light to pass through it, which means that the shadow would not be sharp or distinct.

Option 4 suggests combining an extended source with a transparent screen. Similar to option 2, this combination would result in a larger, less defined shadow due to the characteristics of an extended source.

In conclusion, option 1 is the correct answer because a point source combined with an opaque screen would produce the sharpest shadow of an opaque object.