Answer : 2. "2"
Explanation :

contains will replace contain because – The fifth and final act (Main Subject) is in Singular. Hence, the Verb will also be in Singular as a Verb agrees with its Subject in Number. Singular Subject ® Singular Verb (Main Verb + S) Plural Subject ® Plural Verb (Main Verb without S) Look at the example given below: The great poet and scholar is dead. Here, scholar and poet refer to the same man. So, the Subject is in Singular and the Verb is also in Singular.