During which period did humans first appear on Earth? Quaternary
Neogene
Paleogene
Cenozoic​

1. what is the measure of ∠abc? what is the measure of ∠abd?

Determine whether the following statements are true and give an explanation or counterexample. bold a. when using the shell method, the axis of the cylindrical shells is parallel to the axis of revolution. bold b. if a region is revolved about the y-axis, then the shell method must be used. bold c. if a region is revolved about the x-axis, then in principle it is possible to use the disk/washer method and integrate with respect to x or the shell method and integrate with respect to y.

Need 50 will mark brainliest answer. find the lengths of all the sides and the measures of the angles.