Final answer:
The correct answer to where two or more grounding electrodes create a system is 'a. two'. For the electric-field lines question, a +20 nC charge would emit 20 field lines. There are two types of electric charge: positive and negative.
Step-by-step explanation:
When two or more grounding electrodes are bonded together, a grounding electrode system is established. This means that the correct answer to the fill-in-the-blank question is 'a. two'. Grounding is a safety measure that helps to prevent electric shocks from electrical systems by providing a path for excess electrical charge to flow safely into the ground. The concept of grounding can be related to the grounding process illustrated in Figure 5.13, where a metal sphere is grounded to allow excess charge to flow to Earth, thereby fixing the potential of the conductor at zero volts.
Addressing the referenced information, where it's asked how many electric-field lines should come out of a +20 nC charge if five lines come out of a +5 nC charge; the number of field lines represents the magnitude of the charge. Based on this proportional relationship, if a +5 nC charge emits five field lines, then a +20 nC charge should emit four times as many, that is, 20 field lines (i.e., answer 'd. 20 field lines').
Regarding the types of electric charge, there are two types which are positive and negative (answer 'b. two types'). The two main electrical classifications of materials based on the mobility of charges through them are insulators and conductors.