Final answer:
The keyboard shortcut for transposing the character before the cursor with the character under the cursor is Ctrl+T, which is used in Unix-like text editors and IDEs to swiftly correct character placement (option A).
Step-by-step explanation:
The keyboard shortcut that transposes the character before the cursor with the character under the cursor is Ctrl+T. On most text editors and IDEs that operate in a Unix-like environment, pressing Ctrl+T will cause the immediate two characters - the one before the cursor and the one underneath it - to swap places.
To illustrate this, if you had the word "hte" and your cursor was after the letter 'e', pressing Ctrl+T would correct the word to "the". This functionality is particularly useful in programming and text editing for making quick corrections without having to delete and retype characters.
Hence, the answer is option A.