Step 1: Translate the given numbers.
Total runs $=200$; runs by spinners $=160 \dfrac{160}{200}\times 100=80%$ of the runs} were scored by spinners.
Step 2: Test Conclusion I (team composition).
The statement gives information about runs}, not about the number of players}. From 80% of runs scored by spinners, we cannot infer that 80% of the team members} are spinners. Hence, Conclusion I does not follow.
Step 3: Test Conclusion II (openers were spinners).
Nothing is stated about batting order. Spinners could have batted anywhere; openers might or might not be spinners. No necessary implication $$ Conclusion II does not follow.
Step 4: Decide among the options.
Since neither conclusion is logically compelled by the statement, the correct choice is D.
\[
\boxed{\text{(D) Neither I nor II follows}}
\]