Answer:
The correct answer is the option A: They should definitely not invest with this or any other broker who makes cold calls promising unlimited returns or guarantees against losses for an investment.
Step-by-step explanation:
To begin with, the common people should never or at least the major of the times invest in with brokers who call directly to the person without even knowing them, due to the fact that there are plenty of broker who are not even legally registered and therefore that they can promised everything but later give nothing and even more it does not matter a writing condition due to the fact that most of the times there are always broker prepared for this type of situation.