The question asks about the data query limits for two different report types. According to the Huawei NetEco 6000 data retention policy, monthly statistical data is stored and available for query for up to 5 years. While the first part of the question asks about hourly reports (for which data is typically kept for 90 days), the provided options only contain a number that matches the retention period for monthly reports. Therefore, '5' is the correct answer corresponding to the 5-year query limit for monthly statistics reports.

B. 10, C. 20, D. 30: These values do not correspond to the standard data retention periods for either hourly or monthly reports in the NetEco system. The official documentation specifies a 5-year retention for monthly data, making all other options incorrect.

1. Huawei NetEco 6000 V600R008C00 Performance Management User Guide, "Appendix > Data Storage Period". This section explicitly states the data storage durations for different granularities: "Monthly performance data is stored for 5 years," "Daily performance data is stored for 365 days," and "Hourly performance data is stored for 90 days."

2. Huawei iManager NetEco 6000 Technical White Paper, "Performance Management" section. The paper outlines the system's capability to collect and store historical performance data, specifying the retention policies, including the 5-year period for monthly aggregated data to support long-term trend analysis.