Strong electrolytes are those which:
a.) Dissolve readily in water
b.) Conduct electricity in molten state
c.) Dissociate completely into ions at all concentrations
d.) Dissociate into ions at high dilution

Hint: This question is from the electrochemistry topic. This is a multiple choice question in which one or more options may be correct. So, just go through the differences between strong and weak electrolytes. Thus you can arrive at the answer.

Complete step by step solution:
First of all, what is basically an electrolyte? As we know, electrolytes is a substance that produces an electrically conducting solution when dissolved in polar solvent, such as water. The dissolved electrolyte separates into cations and anions, which disperse uniformly through the solvent. An electrolyte is electrically neutral.
Strong electrolyte is an electrolyte which completely dissociates in aqueous solution. That means the option (a) is correct. Since the strong electrolytes consist of cations and anions, it conducts electricity. So, the option (b) is correct. From the definition itself, the strong electrolytes dissociates completely into ions. So, the option (c) is also correct.
Therefore, the correct options are (a), (b) and (c).

Additional Information:
Examples of strong electrolytes are: dilute sulphuric acid, dilute hydrochloric acids, dilute nitric acid, sodium hydroxides, potassium hydroxides, sodium chloride, potassium chloride, etc.
Examples of weak electrolytes are: oxalic acids. Formic acids, acetic acids, ammonium hydroxides, calcium hydroxides, sodium bicarbonate, calcium oxalate, etc.

Note: In this question, option (d) is incorrect because dissociation into ions at high dilution is a characteristic of weak electrolytes. Strong electrolytes will dissociate into ions at all dilutions.