1. Infinitives in the Spanish language end with -er, -ir, or -ar, just like infinitives in English begin with the word to. Having this in mind, the infinitives here are: comprender and pagar.
2. Yo (I) = leí (the word leí means read in the preterite form - the whole sentence means I read (in the past))
3. Ella (she) = abrió (this is the preterite form of the verb abrir which means to open; the whole sentence means - She opened)
4. Ellos (they) = tomaron (tomaron is the preterite form of the verb tomar, which means to take, and here it is used in its plural form; the whole sentence means - They took).