Step 1: Understand the question.
We must find the key that moves to the next column in MS Excel.
Step 2: Picture the grid.
Excel is a grid of rows and columns. Moving right means going one cell across to the next column.
Step 3: Recall the Tab key.
Pressing the Tab key moves the active cell one step to the right, that is into the next column. This speeds up typing across a row.
Step 4: Check the Enter key.
The Enter key moves down to the next row, not across to the next column, so it is not the answer.
Step 5: Check Backspace and Left Arrow.
Backspace deletes characters, and the Left Arrow moves to the previous column on the left, the opposite direction.
Step 6: Conclude.
So the key that moves to the next column is Tab, which is option 4.
\[ \boxed{\text{Tab}} \]