The most accurate disadvantage of writing code in machine language is:
It is extremely difficult for humans to understand.
Writing in machine language is error-prone and not human-readable, making it hard to debug and maintain. The other options regarding efficiency and speed may not necessarily be true, as machine language is actually the most efficient way for a computer to execute instructions, and the speed of programming is not inherently slower than higher-level languages. The statement about relatively few errors is also misleading, as low readability can lead to more errors during development.