Available choices:
[1]. The size of these growths vary widely-from 2.5 to 7 millimetres. They have a gorgeous shine and can help define oaks.;
[2]. This variation is a great start for narrowing down the possible species. All oaks native to north america and europe have a spiral of overlapping scales on the cup.;
[3]. The acorn cup scales are what you typically see on acorn balls. These growths are often purplish-purple in color, and have specific cracks or fissures to them.;
[4]. These growths will look like small parallel bumps surrounding the acorn cup, hiding the acorn cup scales beneath. Be careful not to access these growths with pliers.;Choose from options above and answer: What most naturally follows?

How to identify oaks by the acorns
Examine the acorn cup scales.
The nut of the acorn grows from a woody cup, which may remind you of a hat. The small scales that make up the cup may be thin and flat, or thick and forming wart-like growths (tubercles).
Answer:
[2].