Why do you use "other" in the sentence?

[Omega]

English Grammar Tests, Elementary Level

ESL/EFL Test #113 "Postcard: Appointment", question 4

We arranged to see each ......... on Friday 20th at 7 in the evening.

(a) one
(b) time
(c) other

English Grammar Tests, Elementary Level

ESL/EFL Test #113 "Postcard: Appointment", answer 4

We arranged to see each other on Friday 20th at 7 in the evening.

Correct answer: (c) other

Your answer was: incorrect
We arranged to see each time on Friday 20th at 7 in the evening.
_________________________

I don't understand why do you use "other" in the sentence?

Omega

[Mister Micawber]

.
Each other = one another. Each person saw the other person.
.
_________________
Native English teacher at Mister Micawber's