A class action lawsuit is most similar to what other type of legal advice?

A class action lawsuit allows one or more people to litigate based on:

Which of the following factors is(are) a requirement(s) under Rule 23 of the Federal Rules of Civil Procedure for establishing class action litigation?

John, a resident of Missouri, was involved in a train wreck. The train was owned and operated by Railways, Inc., a corporation established under the laws of New York. Over 40 people were injured in the train wreck, all of whom were paying passengers of Railways, Inc. Among the injured are the following people: Bobby, a resident of New York; Carla, a resident of New Jersey; Charles, a resident of New York; Patricia, a resident of South Carolina. All of the named injured passengers are part of a class action lawsuit being filed by Lewis Lawyer, a class action litigation expert. Lewis wishes to file the case in federal court based on diversity of citizenship. Which of the following individuals, if any, can be named class representative in order to preserve federal jurisdiction?

Caroline suffered from seizures caused by a medical condition she had developed after a car accident. Her physician had recently changed her medication in an effort to reduce the frequency of her seizures to Suppress It, a prescription drug manufactured by Drug, Inc. However, after taking her medication for one week, she began to suffer from psychotic hallucinations. Caroline contacted Lewis Lawyer, a well-known class action attorney whose subspecialty was litigation against pharmaceutical companies. Lewis discovered that 5 other patients who took Suppress It experienced hallucinations like Caroline. However, the remaining 1,000 patients on Suppress It were not affected in this way. Can Lewis bring a class action lawsuit on behalf of Caroline and the other affected patients?

Cheryl is one of 105 workers who were exposed to asbestos while working in a factory. The factory was owned by Contractors, Inc., a company that furnished building materials for the construction of office and factory space. Contractors, Inc. had failed to provide adequate ventilation and protective masks to its workers. Many of the workers like Cheryl had been employed by Contractors, Inc. for over 10 years and had been exposed for that period of time. As a result of their exposure, Cheryl and 49 other employees had developed advanced cases of lung cancer. The other 55 employees had developed a mild form of lung irritation. However, these 55 employees were also injured when a crane owned and operated by Contractors had crashed on top of them, causing severe physical injuries such as broken legs and ribs and concussions. All 105 employees wish to bring a single class action lawsuit against Contractors, Inc. for their injuries. Can a class action lawsuit be brought for these parties?