Which results would show if the invoice table LEFT JOINed the customer table?

a$.)$

All rows from the customer table, regardless of whether they have invoices

b$.)$

Only rows in the customer table that have a matching row in the invoice table, and vice versa

c$.)$

Only rows from the invoice table that have NULL customer$\_$id's

d$.)$

All rows from the invoice table, even those with NULL for the customer$\_$id column