$(a)$ The electron drift speed is estimated to be only a few $mm\; s^{-1}$ for currents in the range of a few amperes. How then is current established almost the instant a circuit is closed?
$(b)$ The electron drift arises due to the force experienced by electrons in the electric field inside the conductor. But force should cause acceleration. Why then do the electrons acquire a steady average drift speed?
$(c)$ If the electron drift speed is so small,and the electron's charge is small,how can we still obtain large amounts of current in a conductor?
$(d)$ When electrons drift in a metal from lower to higher potential,does it mean that all the 'free' electrons of the metal are moving in the same direction?
$(e)$ Are the paths of electrons straight lines between successive collisions (with the positive ions of the metal) in the $(i)$ absence of electric field,$(ii)$ presence of electric field?

(N/A) The electric field is established throughout the circuit almost instantly (at the speed of light),causing a local electron drift at every point. The establishment of a current does not require electrons to travel from one end of the conductor to the other. However,it takes a short time for the current to reach its steady value.
$(b)$ Each 'free' electron accelerates,increasing its drift speed until it collides with a positive ion of the metal. It loses its drift speed after the collision but starts to accelerate again,only to suffer another collision. On average,therefore,electrons acquire a steady drift speed.
$(c)$ This is possible because the electron number density is enormous,approximately $10^{29}\; m^{-3}$.
$(d)$ No. The drift velocity is superposed over the large random thermal velocities of the electrons.
$(e)$ In the absence of an electric field,the paths are straight lines. In the presence of an electric field,the paths are,in general,curved due to the acceleration provided by the field between collisions.