The man-made stone projection discovered at the center of a Neandertha

It is extremely important to read the question properly to know exactly what you are looking for.

"Which of the following, if true, most strongly supports the hypothesis?" - So we are looking for an option that will support our hypothesis. It will make our hypothesis more probable. What is our hypothesis?
"Sundials were developed and used centuries earlier than expected."

What are the premises?
The man-made stone projection discovered at the center of a Neanderthal settlement exhibits every quality of a device capable of indicating the time of day with the shadows cast depending on the position of the sun -- perhaps the earliest sundial ever discovered.

So the researchers have discovered a man made projection. It exhibits every quality a device indicating time with the shadows cast should have. It seems like it is a sundial - the earliest one. Based on this the researchers are hypothesising that sundials were developed much before expected earlier. It seems that the Neanderthals were using sundials. What will strengthen it? If we can show that the man made projection is very likely to be a sundial.

E. The sundial was apparently constructed to indicate the time at the precise latitude where the Neanderthal settlement in which it was found is located.
It says that the projection indicates the time of the precise latitude where it was found. So the construction is such that it indicates time of this latitude. So it seems more likely that it was constructed to tell time here. That it is not just some random construction. That it actually is a sundial. This strengthens our hypothesis that sundials were developed and used centuries earlier than expected.

The only confusing option is (B)

B. No object capable of indicating the time by way of solar positioning has been attributed to an earlier date than the sundial discovered at the Neanderthal settlement.

Note what our hypothesis is: "Sundials were developed and used centuries earlier than expected."
Till recently, it was believed that sundials were developed and used since time X. Now with this discovery at Neanderthal site, we are hypothesising that they were developed and used centuries earlier. How does "no sundial has been attributed to an earlier date than the Neanderthal one" help strengthen our hypothesis? Our hypothesis is "used centuries earlier". It doesn't say that Neanderthals were the first ones to use. Something that helps us establish that sundials were used before time X is helpful to us.

Answer (E)