Which of the following statements is true?
a) when you drive a car, pressing its gas pedal sends a message to the car to perform a task—that is, to go faster.
b) you send messages to an object; each message is implemented as a method call that tells a method of the object to perform its task.
c) a program might call a bank-account object's deposit method to increase the account's balance.
d) all of these statements are true.

Pp 4.1 design and implement a class called sphere that contains instance data that represents the sphere’s diameter. define the sphere constructor to accept and initialize the diameter and include getter and setter methods for the diameter. include methods that calculate and return the volume and surface area of the sphere (see pp 3.5 for the formulas). include a tostring method that returns a one-line description of the sphere. create a driver class called multisphere, whose main method instantiates and updates several sphere objects.