NAD $27$ horizontal coordinates differ from NAD $83$ because of what?

Group of answer choices

NAD$27$ uses an ellipsoid that best fits North America and NAD $83$ uses a global ellipsoid

NAD$27$ was done using older surveying equipment and NAD $83$ was done using GPS

NAD$83$ ellipsoid is GRS$80,$ but GPS uses WGS$84$ a slightly corrected ellipsoid

NAD$27$ and NAD$83$ only differ about $1\mathrm{.}5$m