En las playas de Honduras, ________ (prohibir-4 palabras) durante el día

The correct answer is “creen”

The correct answer to your question is:

Es improbable que muchas personas crean en la medicina tradicional.

Hope this answer has helped you. If it has, please mark this answer as brainliest. Thanks.

Have a wonderful day.

Sadly, there's not really a trick to learn how to conjugate. It's mostly by memorizing. 
There are many ways of conjugating. When conjugating a verb from infinitive to present tense, you have to check if the verb ends with -ar, -er, -ir, -or.
Cerrar ends with -ar, in this case. 
Yo        cierro (add -o)
Tú        cierras    (add -as)  
Usted [or el/ella]    cierra ( -a)
Nosotros      cerramos (-amos)
Ellos [or ustedes]    cierran (-an)

(I recommend you google it since it's really difficult to explain.)

(Here are the answers to your assignment)
1. Ustedes cierran
2. Tú cierras
3. Nosotras cerramos
4. Mi hermano cierra
5. Yo cierro
6. Usted cierra
7. Los chicos cierran
8. Ella cierra

Dormir
Dormir ends with -ir, so it's different. (Not that different though)
Yo        duermo (add -o)
Tú        duermes   (add -es)  
Usted [or el/ella]    duerme ( -e)
Nosotros      dormimos (-imos)
Ellos [or ustedes]   duermen (-en)

(Here are the answers to your assignment)

1. Mi abuela no duerme
2. Yo no duermo
3. Tu no duermes
4. Mis hijos no duermen
5. Usted no duerme
6. Nosostros no dormimos
7. El no duerme
8. Ustedes no duermen

I hope I was able to help a little! Good luck, have a brainly day!