Segue abaixo a descrição dos packages citados na alternativa A:
Java Platform, Standard Edition 7 - API Specification
java.lang: Provides classes that are fundamental to the design of the Java programming language.
java.io: Provides for system input and output through data streams, serialization and the file system.
java.nio: Defines buffers, which are containers for data, and provides an overview of the other NIO packages.
java.math: Provides classes for performing arbitrary-precision integer arithmetic (BigInteger) and arbitrary-precision decimal arithmetic (BigDecimal).
java.net: Provides the classes for implementing networking applications.
java.util: Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).
Fonte: https://docs.oracle.com/javase/7/docs/api/