#### Answer

The matching numbers and letters are given as follows:
a: 4
b: 7
c: 16
d: 18
e: 1
f: 2
g: 8
h: 3
i: 5
j: 15
k: 6
l: 11
m: 13
n: 10
o: 14

#### Work Step by Step

The explanation for each letter are as follows:
a: A node is the point where multiple wires/elements of the circuit meet. Thus, $\fbox{4}$ is the best option.
b: What is described in description 7 is a closed path, which is a loop. Thus, $\fbox{7}$ is the best option.
c: Kirchhoff's Voltage Law (KVL) states that the sum of the voltages of a closed path in a circuit is 0. Thus, $\fbox{16}$ is the best option.
d. Kirchhoff's Current Law (KCL) states that the sum of the currents into the junction equals the sum of the currents out of a junction. Thus, $\fbox{18}$ is the best option.
e. Ohm's law states that $V=IR$. Thus, $\fbox{1}$ is the best option.
f. In a passive reference configuration, the current enters through the positive side (which is the side of higher potential). Thus, $\fbox{2}$ is the best option.
g. An ideal conductor has no resistance, meaning that the voltage is 0. Thus, $\fbox{8}$ is the best option.
h. No current can flow in an open circuit, for there is no connection that allows the current to get back to the current or voltage source. Thus, $\fbox{3}$ is the best option.
i. A current source supplies a constant current to the circuit. Thus, $\fbox{5}$ is the best option.
j. Voltages across parallel branches of a circuit are always equal. Thus, $\fbox{15}$ is the best option.
k. A controlled source depends on the current and voltage elsewhere in the circuit. Thus, $\fbox{6}$ is the best option.
l. Voltage is energy per unit charge. Thus, $\fbox{11}$ is the best option.
m. Current is the amount of charge that passes through over time. Thus, $\fbox{13}$ is the best option.
n. Resistance is in Ohms, which is the same as Volts per Amp. Thus, $\fbox{10}$ is the best option.
o. Currents through series elements are always equal. Thus, $\fbox{14}$ is the best option.