Answer: TCP/UDP Network

The question asks for a load balancer that preserves client IP addresses by default when using the Standard network tier. Based on Google Cloud documentation and the community discussion consensus (with multiple comments upvoted and referencing official sources), the TCP/UDP Network load balancer (Option D) is the correct choice. It is a non-proxied load balancer that preserves client IP by default and is supported in the Standard network tier. Option A (SSL Proxy) and Option B (TCP Proxy) are proxied load balancers that terminate client connections and do not preserve client IP by default, and they require the Premium network tier. Option C (Internal TCP/UDP) does preserve client IP but is only supported in the Premium network tier, making it unsuitable for the Standard tier requirement. The community discussion strongly supports D, with comments highlighting the network tier compatibility and client IP preservation.

Author: LeetQuiz Editorial Team