Final answer:
The subject is Computers and Technology, and the question is about Cisco proprietary API and its use in configuring network devices.
Step-by-step explanation:
The subject of this question is Computers and Technology. Specifically, it is about the different automation tools used in networking. The question mentions Cisco proprietary API, which is a technology used to configure network devices. The options given are:
a. OnePK
b. OpenFlow
c. OpFlex
d. NETCONF
Out of these options, the correct answer is OnePK. OnePK is a Cisco proprietary API that uses Java, C, or Python to configure network devices. It can use either SSL or TLS to encrypt data in transit. OpenFlow is a different automation technology used in software-defined networking, OpFlex is a policy protocol for Cisco's Application Centric Infrastructure (ACI), and NETCONF is a network management protocol.