Spiders use their silk to build strong webs, to trap bugs, to save themselves from falling, to wrap their eggs safely, and even to glide through the air. How can one material—spider silk—be used for so many different ?

The missing word is things.

However, the real question is how one material can serve so many purposes? That is what makes it possible for the spiders web to have a high "utility" value?

The answer is in how the spiders make the silk.

Explanation:

So it interesting to note that spiders do not make only one kind of silk. They vary depending on what purpose it's doing serve.

The most common type is Dragline Silk.

Dragline Silk: This contains spidroins. Spidroins fall under a category of a protein called scleroproteins. Because of its composition, a strand or fiber of Dragline has the same tensile strength as steel albeit more flexible. That is if one produced steel the diameter of a spider's silk, and compared both for strength, the silk will be stronger.

The spider produces Dragline silk in its silk glands where they are as viscous as a paste. From here is pulled out or extruded into lines of silk.

Other types of spider silk are:  

Cheers

the answer would be d : p