The main objective of the Java Security Model ( JSM) is to:

A.
Provide accountability for events

B.
Protect the user from hostile, network mobile code

C.
Protect the local client from user-input hostile code

D.
Protect a web server from hostile, client code

Explanation:
When a user accesses a Web page through a browser, class files for
an applet are downloaded automatically, even from untrusted
sources. To counter this possible threat, Java provides a
customizable sandbox to which the applets’ execution is confined.
This sandbox provides such protections as preventing reading and
writing to a local disk, prohibiting the creation of a new process,
prevention of making a network connection to a new host and
preventing the loading of a new dynamic library and directly calling
a native method. The sandbox security features are designed into the
Java Virtual Machine (JVM). These features are implemented through
array bounds checking, structured memory access, type-safe
reference cast checking to ensure that casting to an object of a
different type is valid, and checking for null references and
automatic garbage collection. These checks are designed to limit
memory accesses to safe, structured operations.
The other answers are distracters.