🔍 Key Concepts

• Difference between primary and secondary batteries in terms of recharging • Typical electrolyte type (acid vs alkaline) used in nickel–cadmium (Ni-Cd) batteries • How wet-cell nickel-cadmium storage batteries are commonly constructed on vessels

💭 Think About

• First, decide: is a nickel–cadmium storage battery something that is normally recharged, or is it a one‑time‑use battery? That will tell you whether it is primary or secondary. • Next, think about the usual electrolyte in nickel–cadmium batteries: is it more like the sulfuric acid used in lead‑acid batteries, or is it based on an alkaline solution such as potassium hydroxide? • Eliminate any options that combine the wrong recharge type with what you know about how Ni‑Cd batteries are used in marine systems (e.g., emergency lighting, communications, etc.).

✅ Before You Answer

• Confirm whether storage battery in marine usage typically means a rechargeable (secondary) battery. • Recall that lead‑acid batteries use acid electrolyte; compare that to what you know about nickel–cadmium chemistry. • Before choosing, verify that your option matches both: the correct electrolyte type (acid vs alkaline) and the correct cell type (primary vs secondary).