Which of the following terms best describes a cloud service's ability to rapidly increase user accounts?

Which of the following terms best describes a cloud service's ability to rapidly increase user accounts?

• Volatility
• Viability
• Elasticity
• Synchronicity 

EXPLANATION

 In cloud computing, elasticity is defined as "the degree to which a system is able to adapt to workload changes by provisioning and de-provisioning resources in an autonomic manner, such that at each point in time the available resources match the current demand as closely as possible"