How should you design this schema?

You are designing a schema for a Cloud Spanner customer database. You want to store a phone number array field in a customer table. You also want to allow users to search customers by phone number.

How should you design this schema?
A . Create a table named Customers. Add an Array field in a table that will hold phone numbers for the customer.
B . Create a table named Customers. Create a table named Phones. Add a CustomerId field in the Phones table to find the CustomerId from a phone number.
C . Create a table named Customers. Add an Array field in a table that will hold phone numbers for the customer. Create a secondary index on the Array field.
D . Create a table named Customers as a parent table. Create a table named Phones, and interleave this table into the Customer table. Create an index on the phone number field in the Phones table.

Answer: C