For this case what we should do is fill in the blank with the correct comparison adjectives.
The structure that we must follow is:
Person 1 + more/less + adjective + than + Person 2
Person 1 + is + as + adjective + as + Person 2
We have then:
A) La iguana es fea. La serpiente es muy fea. La serpiente es más fea que la iguana.
A) The iguana is ugly. The snake is very ugly. The serpent is uglier than the iguana.
B) Julio es alto. Pablo es muy alto. Pablo es mas alto que Julio.
B) Julio is tall. Pablo is very tall. Pablo is taller than Julio.
C) La iguana es fea. La serpiente es muy fea. La iguana es menos fea que la serpiente.
C) The iguana is ugly. The snake is very ugly. The iguana is less ugly than the snake.
D) Anita es alta. (5'10") Susana es alta también. (5'10") Anita es tan alta como Susana.
D) Anita is tall. (5'10 ") Susana is also tall (5'10") Anita is as tall as Susana.
E) Juan es alto. María es muy alta. María es mas alta que Juan.
E) Juan is tall. Maria is very tall. Maria is taller than Juan.
F) Juan es alto. María es muy alta. Juan es menos alto que María.
F) Juan is tall. Maria is very tall. Juan is less tall than Maria.