Answer:
C) He should connect four 1-Ohm resistors in series
Explanation:
If there are n resistors connected in series, say [tex]R_1, R_2,...R_n[/tex], the total resistance of the connection is the sum of the individual resistances, ie for a series combination of n resistors, the following holds;
[tex]R_T=R_1+R_2+...+R_n.................(1)[/tex]
where [tex]R_T[/tex] is the total resistance.
Since the student needs a 4-Ohm resistor and the only available ones are 1-Ohm each, he should combine each of them in series.
[tex]R_T=1+1+1+1\\R_T=4-Ohms[/tex]