Analyze and compare the effectiveness of three distinct landing page structures: a classic above-the-fold structure emphasizing a clear value proposition and call-to-action; a benefit-driven structure highlighting customer testimonials and social proof; and a multi-step structure guiding users through a series of progressively engaging sections.  For each structure, consider the following aspects: conversion rate optimization techniques employed;  visual hierarchy and user experience design;  A/B testing opportunities;  SEO considerations;  mobile responsiveness;  and overall effectiveness in achieving a specific marketing goal (e.g., lead generation, sales, sign-ups).  Provide a comparative analysis outlining the strengths and weaknesses of each structure,  including specific examples of best practices and potential pitfalls. Conclude with recommendations on which structure is most suitable for different business objectives and target audiences. The analysis should be supported by relevant data and research where possible, focusing on practical applications and real-world examples.