The perfect tense is made of the verb haber and a past participle. Some verbs have irregular past participles. Irregular past participles include: dicho (said), hecho (done) and visto (seen).

Subject pronouns are not always needed when using verbs in Spanish. This video shows how to use verbs in the present tense in Spanish.

The review and approval timeline is approximately 45 days. Taiwan uses central and local ethics systems. Multi-site studies use the centralised systems. However, the individual research ...