The correct answer is 'Notifications about emerging regulatory requirements for online data handling specific to the European market.' This answer is the most relevant because the e-commerce platform is now operating within the European Union, which means it is subject to EU data handling and privacy laws, such as the GDPR. Non-compliance could lead to significant fines and legal issues, along with reputational damage. As such, threats or changes regarding these laws are integral to the business operation and must be a priority. The other options, while potentially important, are less immediately relevant to the company's European operations: 'Detailed reports about mobile malware trends in Asia-Pacific regions' are geographically irrelevant; 'Algorithms for detecting anomalies in virtual private network (VPN) traffic' offer a security measure that could be globally relevant but doesn't have specific implications for the new EU operations; 'Broad threat landscape summaries for the retail sector in Q1' offer useful contextual information, but lack the immediacy and specificity required for prioritizing actions related to the business's geographic expansion.