Institution: Bangladesh Bank Exam: অফিসার (ক্যাশ ) - Sonali | Rupali | BD Krishi | Rajshahi Krishi Unnayn | Investment Corporation Of Bangladesh - ২৯. ০৩.২০১৯ ||
Topic: Computer (কম্পিউটার), Subject: Computer and ICT (তথ্য ও যোগাযোগ প্রযুক্তি)

Best Answer Explained in Below-:

In Excel, when entering a formula in a cell, it is essential to start with an equals sign (`=`). This symbol is a clear indicator to Excel that the user intends to input a formula rather than plain text or numbers. When you begin a cell's input with `=`, Excel knows to evaluate the expression that follows it.

For example, typing `=A1 + B1` tells Excel to add the values found in cells A1 and B1, and then display the result in the cell where the formula is entered. If you omit the `=`, Excel interprets the input as text. For instance, entering `A1 + B1` without the equals sign would simply display that string in the cell, rather than computing a sum.

The other options provided—`$`, `@`, and `#`—have specific functions in Excel, but they do not indicate the beginning of a formula. The dollar sign (`$`) is used for absolute references, the at sign (`@`) typically refers to structured references in tables, and the hash sign (`#`) indicates errors or a range of cells, but none of these can initiate a formula. Thus, `=` is the correct and necessary symbol to signal that you are entering a formula.