What does auto type specifier do in this line of code (since C++11)?

auto x = 4000.22;

• It specifies that the type of x will be deduced from the initializer – in this case, double.
• It specifies that the type of x is automatic meaning that if can be assigned different types of data throughout the program.
• It specifies that x is a variable with automatic storage duration.
• It specifies that more memory will be allocated for x in case it needs more space, avoiding loss of data due to overflow.