When you have a form with a multiple-choice or drop-down question with more than one answer selected, the answers are displayed in the same cell, separated by commas.
When you export all your results as a CSV file, your results will also be in the same row and column, like this:
You can split the results by highlighting the cells you would like to separate, by clicking Data → then clicking on the Split text to columns option. This will automatically try to detect the items to be separated and move them to new columns.
You also have the option to select the separator type by commas, semi-colons, periods, and spaces.
If you’d like the answers to be divided into separate columns, here’s how to do this using Google Sheets and Excel:
See this Google help article for more information.
See the instructions for excel here.