Answer:
double subtotal = Double.parseDouble(subtotalString);
Step-by-step explanation:
Required
Determine which method converts string object to double variable
From the question;
The string object is: subtotalString
The double variable is: subtotal
From the given options (a) to (d), the option that answers the question is:
double subtotal = Double.parseDouble(subtotalString);
And it follows the syntax:
[datatype] [variable-name] = [Data-type].parse[Datatype]([string-variable])