Question

1. Mt. McKinley is the highest.

2. Mt. McKinley is highest.
3. Mt. McKinley is higher than any other mounttain in the USA.

4. Mt. McKinley is the highest of all the mountains in the USA.

5. Mt. McKinley is highest of all the mountains in the USA.

6. Mt. McKinley is the highest mountain of all the mountains in the USA.

7. Mt. McKinley is highest mountain of all the mountains in the USA.

(Which ones are ungrammatical?)

Answer 1

1 - 6 are grammatically correct, but 1 - 4 and 6 are the best. 7 is correct except for the need the "the" as in 6.