A writer can effectively engage readers using an observation by creating vivid imagery that evokes emotions or curiosity. In this context, option A stands out as a compelling choice.
A. by describing a scene where heavy rain clouds block the sun's light over an eerie pond
This option provides a rich visual description that can draw readers in, allowing them to visualize the scene and feel the mood. The use of "heavy rain clouds" and "eerie pond" suggests an atmosphere that is both foreboding and intriguing, prompting readers to explore what might happen next or the underlying significance of the setting.
In contrast, options B, C, and D lack the same level of vivid observational detail that could engage readers' senses and emotions in a direct way. While all options have potential, the descriptive imagery in option A is particularly effective for engaging an audience.