Final answer:
R is a programming language that is available for both Mac and Windows computers. It is free to use and can be used for data manipulation even with code bugs. Individuals can contribute new code to R through packages and extensions.
Step-by-step explanation:
R is an open source programming language that is used for statistical computing and graphics. It is available for both Mac and Windows computers, so statement a is true. R is free for all users to download and use, making statement b true. However, individuals can contribute new code to R through packages and extensions, so statement c is not true. Lastly, R can be used for data manipulation and analysis, even when there are code bugs, so statement d is also true.