can I replace nulls in a PIVOT with zeroes?
If you have the following table of data that you want to pivot:

CREATE TABLE yourtable (id int, name varchar2(1), value varchar(10));

INSERT ALL 
    INTO yourtable (id, name, value )
         VALUES (1, 'A', '1500')
    INTO yourtable (id, name, value )
         VALUES (1, 'B', '4500')
    INTO yourtable (id, name, value )
         VALUES (2, 'C', '3.5')
    INTO yourtable (id, name, value )
         VALUES (3, 'B', 'test')
    INTO yourtable (id, name, value )
         VALUES (4, 'A', 'blah')
    INTO yourtable (id, name, value )
         VALUES (4, 'C', 'hello')
SELECT * FROM dual;


And your current code is similar to:

select id, OptionA, OptionB, OptionC
from
(
  select id, name, value
  from yourtable
) src
pivot
(
  max(value)
  for name in ('A' as OptionA, 'B' OptionB, 'C' OptionC)
) piv


See SQL Fiddle with Demo.  The sample data will create null values. 

When you want to replace the null values you have to do it in the final SELECT list. So your code will need to be:

select id, 
  coalesce(OptionA, '0') OptionA, 
  coalesce(OptionB, '0') OptionB, 
  coalesce(OptionC, '0') OptionC
from
(
  select id, name, value
  from yourtable
)
pivot
(
  max(value)
  for name in ('A' as OptionA, 'B' as OptionB, 'C' as OptionC)
);


See SQL Fiddle with Demo