What is the default value of column?

Answer: Option A

In MySQL, when you create a new table and define a column, it often needs a starting value. This is called the default value.

This question asks about the default value if you don't explicitly specify one for your column.

The answer is Option A: NULL.

Here's why:
* NULL means "no value" or "unknown". It's the most common default in MySQL.
* 0 is a specific value, not the default.
* -1 is also a specific value, not the default.
* Undefined is not a valid default value in MySQL.

Think of it like this: If you create a column for "age" and don't provide a default, MySQL will set the age to NULL for new rows until you provide a value.

Key Takeaway: When you create a column in MySQL and don't specify a default value, the column will automatically have a NULL value.