Within Veeam Backup & Replication, the functionality that achieves the lowest Recovery Point Objective (RPO) is B: Continuous Data Protection (CDP). CDP is designed to protect critical workloads by continuously capturing changes and replicating them to a target site, allowing for very low RPOs, often measured in seconds. This is achieved through the use of VMware's vSphere APIs for I/O Filtering (VAIO), which intercepts and replicates I/O streams almost in real- time. CDP is particularly valuable for applications that require high levels of availability and cannot tolerate significant data loss. By providing near-continuous replication, CDP ensures that in the event of a failure or disaster, data loss can be minimized to a very narrow window, significantly reducing the potential impact on business operations.

Explanation
A backup proxy is a component that acts as a data mover in the backup infrastructure. It retrieves data from the source and transfers it to the target1. When defining a replica job, it is recommended to have at least one backup proxy server in each site to enable a stable connection for VM data transfer across sites2. This way, the backup proxy at the source site can communicate with the backup proxy at the target site and send data over the WAN without affecting the production hosts2. The other options are not correct for explaining why backup proxies are recommended. The proxies do not allowautomatic WAN acceleration, as this is a function of the WAN accelerators3. The proxies do not allow for no VM snapshots during transit, as the replication process requires creating a snapshot of the source VM to read its data. The proxies do not allow replication automatic restart after failure, as this is a setting of the replication job.
References1: Backup Proxy.2: Replication Architecture.3: WAN Acceleration.: [Replication Process].:
[Replication Job Settings].

Archive tier is an additional tier of storage that can be attached to a scale-out backup repository.
You can transport data to the archive tier for archive storage from the following extents:
From performance extents that consist of Amazon S3, Microsoft Azure or S3 compatible with data archiving object storage repositories.
From capacity extents.
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It is not required to have a capacity tier before using archive tier.
https://helpcenter.veeam.com/docs/backup/vsphere/archive_tier.html?ver=120

Explanation
https://helpcenter.veeam.com/docs/agentforwindows/userguide/backup_chain.html?ver=40