Depend on what is your target audience. If they are beginner comp sci students then D is ok. Preferably something lispy like Racket. If they are more of "learn to code" and get high paying job, D is not recommended. Python, Java/Kotlin, R, C# or C/C++ would be better choices. If you are focusing on embedded students, C is a must and maybe Rust. If you are focusing on web development, then Javascript/Node is a must. Some people would argue that learning any languages is ok as you learn the concept. But this argument is the same as learning Japanese or Korean so you have "upper hand understanding" of Chinese. Why not just go straight learn Chinese than beating around the bush learning something "similar". There are concepts in C/C++ that are hard to replicate in C# or Python such as pointers and low level memory management. Or, data science community on Python platform that are scarce in others. Same with r for statistics, C# for .Net/Microsoft, Java/Kotlin for Android stuff. Most people have limited ability to learn 1 or 2 languages over their lifetime. Just focus on that most useful and accessible. Good one will always go on and create their own languages.