I need help with this.

1. In a bash shell script, what are the required elements of an "if" control structure? 2. In a bash shell script, what are the optional elements of an "if" control structure? 3. In a bash shell script, what are the required elements of a "while" control structure? 4. What is the difference between a shell variable and environment variable? Which one is considered local and which is considered global? 5. List the four kinds of shell parameters/variables.