The correct answer is A) The specific gravity of the electrolyte will be generally unaffected by the state of charge. This is because the specific gravity of the electrolyte in a nickel-cadmium battery is not significantly affected by the state of charge. The specific gravity remains relatively constant throughout the charging and discharging cycles, unlike lead-acid batteries where the specific gravity changes. The other options are incorrect: B) Extended trickle charging should be avoided - This is true, as extended trickle charging can cause overcharging and damage to the battery. C) Add distilled water just prior to charging to insure proper mixing - This is not necessary, as the electrolyte in a nickel-cadmium battery is already well-mixed. D) The charging rate should never allow gassing - This is not entirely correct, as a small amount of gassing is normal and expected during the charging process.