Final answer:
The command 'expr' is used in Shell to evaluate mathematical expressions, primarily suited for integer arithmetic. For more complex calculations, such as those involving scientific notation, other tools like 'bc' or programming languages are used.
Step-by-step explanation:
The Shell command used to evaluate a mathematical expression is d) expr. This command is typically used in Unix and Unix-like operating systems to perform integer arithmetic operations. For example, if you want to evaluate the expression '4 + 5', you can type expr 4 + 5 into the command line, and it would return the result '9'. It's important to note that this command does not support floating-point (decimal) arithmetic directly, so it is not suitable for calculating scientific notation directly. Instead, you would use command line tools like 'bc' or programming languages such as Python for more complex calculations that involve floating-point numbers or scientific notation.