Final answer:
The best strategy for Mr. Nguyen to aid an English-language learner struggling with oral instructions is to provide written instructions, rephrase key information, and allow more time for processing.
Step-by-step explanation:
If Mr. Nguyen notices that his English-language learner is struggling to understand verbal instructions, the most effective strategy he could employ is to provide the student with written instructions. This would allow the student to have a reference to look back on which can aid in understanding and retaining the information. To further enhance listening comprehension, Mr. Nguyen could also consider using methods such as rephrasing key steps and instructions or giving the student additional time to process what is being said.