Explanation
According to the Strategic Themes article on the Scaled Agile Framework website, strategic themes are portfolio-level business objectives that provide competitive differentiation and strategic advantage. They provide business context for portfolio strategy and decision-making, representing aspects of the enterprise's strategic intent. Strategic themes are best stated in Objective and Key Result (OKR) format. Written in plain business language, these OKRs say what the portfolio will pursue, thus providing decision-makers and contributors at all levels the clarity needed for decentralized decision-making. Therefore, the correct answer is D, create a 'one-stop shop' for all citizen-facing services provided by the agency. This is a good example of an agency strategic theme, as it expresses a clear and measurable goal that aligns with the agency's vision and mission. The other options are not accurate, as they are not good examples of agency strategic themes. Comply with agency development lifecycle regulations (A) is not a strategic theme, but a compliance requirement that applies to all solutions. Reduce agency IT spend (B) is not a strategic theme, but a cost-cutting measure that does not reflect the value proposition of the agency. Improve cost and schedule performance of IT projects is not a strategic theme, but a project management metric that does not capture the business outcomes of the solutions.