Invalid File Mode: 'rw'

Explanation:
In computer programming, a file mode is a parameter used when opening or creating a file to specify the intended operations on the file. It determines whether the file should be read from, written to, or both. The file mode is usually represented by a combination of characters that define the permissions and access rights for the file.

The valid file modes in most programming languages include the following:

1. Read Mode ('r'): This mode allows the program to read data from the file. It is used when you want to open a file for reading purposes only. The file must already exist, otherwise, an error will be thrown.

2. Write Mode ('w'): This mode allows the program to write data to the file. If the file does not exist, it will be created. If the file already exists, its contents will be truncated (erased) before writing new data to it.

3. Append Mode ('a'): This mode allows the program to append data to the end of an existing file. If the file does not exist, it will be created. Unlike the write mode, the existing contents of the file are preserved, and new data is added at the end.

4. Binary Mode ('b'): This mode is used to open a file in binary format, which is necessary when dealing with non-text files such as images, audio, or video files. It is often used in conjunction with the read or write modes.

Invalid File Mode: 'rw'

The 'rw' file mode mentioned in option D (rw) is not a valid file mode. A file mode can be either 'r', 'w', or 'a' to specify the read, write, or append operations, respectively. Combining 'r' and 'w' together as 'rw' does not represent a valid file mode. Therefore, option D is the correct answer as it denotes an invalid file mode.