Help explaining some practice test questions

im studying for an electronics certification exam and I had a few problems I need help explaining. I have attached 4 screenshots of the questions I need an explanation for and how to slove them.hopefully explained in a way that's easy to remember. the questions are #46, #53,#73, and #90. the correct answers respectively are B,A,D, and D.

heres the fourth screenshot

46: VC > VB > VE. For the transistor to be conducting, VB > VE. For the transistor to be bias correctly, VC > VE; if VC < VE, the transistor is saturated. See https://en.wikipedia.org/wiki/Bipolar_junction_transistor#Regions_of_operation
53: use Ohm's law to find the current through R1. Use Ohm's law to find the resistance of R2 given the current through R1 and the load.
73: https://en.wikipedia.org/wiki/Amplifier#Class_C
90: the modulus is the number of counts. Each stage doubles the number of counts in a binary counter.