Answer:
The most important reason for an accountant to secure a spreadsheet is option C: it protects the client's information.
Accountants often deal with sensitive financial information about their clients, including personal and financial data that should be kept confidential. If a spreadsheet containing this information is not secured properly, it could be accessed or manipulated by unauthorized individuals, leading to serious consequences such as identity theft, fraud, or data breaches. Therefore, securing a spreadsheet is crucial for protecting the privacy and security of a client's information.
Option A (creating the right type of formatting) and Option D (assisting in forecasting) are not directly related to the need to secure a spreadsheet, although they may be important aspects of spreadsheet design and use. Option B (allowing them to be altered later on) is actually the opposite of what securing a spreadsheet aims to achieve, which is to prevent unauthorized changes to the data.