Final answer:
The expressions, organized from greatest to least by number of terms, are: x²yz, 3xyz, 2x²y - 3x⁴, 9x²yz. The correct order is i, ii, iii, iv.
Step-by-step explanation:
The expressions, organized from greatest to least by number of terms, are:
x²yz
3xyz
2x²y - 3x⁴
9x²yz
Therefore, the correct order is i, ii, iii, iv.