Question

Choose the past participle for the Spanish verb abrir.

Answer 1

C. Abierto. 
The past participle is the tense with -ed, but abrir is one of the irregulars.

Answer 2

Right answer: abierto

Past participles are those that can be used as adjectives or used to form verb tenses.

Now, abrir (to open) is an irregular verb in Spanish (Castilian) and its verbal tense in past participle is abierto (opened). In this case it may be used as an adjective.

The other options are incorrect because:

-abría is the verb abrir (to open) conjugated in preterite imperfect indicative with the 1st person in singular yo (I).

-abrido is grammatically incorrect.

-abrió is the verb abrir (to open) conjugated in simple past with the 3rd person in singular él/ella/eso/esa (he/she/it).