Final answer:
A nurse should have calcium gluconate available when administering magnesium sulfate for severe preeclampsia, as it serves as an antidote for magnesium toxicity.
Step-by-step explanation:
The nurse should have calcium gluconate which is option a. readily available for a client who is receiving magnesium sulfate to treat severe preeclampsia. Calcium gluconate acts as an antidote to counteract the potential toxic effects of magnesium, such as magnesium toxicity, which can occur due to the administration of magnesium sulfate. It is important for the nurse to monitor the patient's condition and have the appropriate treatment available in case of magnesium overdose.