check my answears please:

In Java an array can only store one type of data. TRUE

$2.$ An array index cannot be a float, double, boolean, or String. TRUE

$3.$ A Java main method uses the parameter $($String$[]$ variable$)$ so that a user can run the program and supply command$-$line parameters. Since the parameter is a String array, however, the user does not have to supply any parameters. TRUE

$4.$ Interface classes cannot be extended but classes that implement interfaces can be extended. FALSE

$5.$ A derived class has access to all of the methods of the parent class, but only to the protected or public instance data of the parent class. FALSE

$6.$ Consider the following class hierarchy:

A is a derived class of X$?$ FALSE

$7.$ Y is a derived class of Z$?$ FALSE

$8.$ If A$,$ B$,$ Y and Z all contain the same instance data d$1,$ then d$1$ should be declared in X and inherited into Y$,$ Z$,$ A and B$.$ TRUE

$9.$ The reserved word, extends, is used to denote a has$-$a relationship. FALSE

$10.$ You may use the super reserved word to access a parent class's private members. FALSE

$11.$ Java doesn't support multiple inheritance; but it does support the implementation of multiple interfaces. TRUE

$12.$ To swap the $3$rd and $4$th elements in the int array values, you would do: FALSE

values$[3]=$ values$[4]$;

values$[4]=$ values$[3]$;

$13.$ A polymorphic reference can refer to different types of objects over time. TRUE

$14.$ Java allows one to create polymorphic references using inheritance and using interfaces TRUE

$15.$ A reference variable can refer to any object created from any class related to it by inheritance. TRUE

$16.$ The fact that the System.out.println$()$ method is able to handle such a wide variety of objects, and print them correctly, is an example of the polymorphic nature of the println$()$ method. TRUE

$17.$ An interface reference can refer to any object of any class that implements the interface. TRUE

$18.$ An class reference can refer to any object of any class that descends from the class. TRUE

$19.$ A method's parameter can be polymorphic, giving the method flexible control of its arguments. TRUE

$20.$ One of the advantages of the linear search is that it does not require its data to be sorted. TRUE