Dynamic visualizations can make unseen phenomena such as chemical reactions visible but students need guidance to benefit from them. This study explores the value of generating drawings versus selecting among alternatives to guide students to learn chemical reactions from a dynamic visualization of hydrogen combustion as part of an online inquiry unit. In prior research, generation has been more successful than selection in helping students distinguish among ideas to learn complex topics. However, selecting among perplexing alternatives may motivate learners to distinguish among ideas they might otherwise neglect. To test the value of selection for helping students distinguish ideas, this study contrasted "complex selection" (involving normative as well as non-normative ideas identified in prior research) from "typical selection" (involving images from the visualization). Results showed that all conditions improved student understanding and that "typical selection" was less effective than "generation" while "complex selection" was as successful as "generation." In both "generation" and "complex selection" students revisited the visualization while learning, whereas revisiting was rare in "typical selection." These results support the idea that distinguishing among common non-normative ideas is more valuable than distinguishing among images from the visualization. In addition, for students with low prior knowledge, both "generation" and "complex selection" had some advantages. Overall, the results suggest that students learning from complex visualizations could benefit from a combination of "complex selection" and "generation."