The 'a' personal in Spanish is used to give the verb a subject that it acts upon. When preceding a masculine noun, 'a' changes to 'al' and replaces the 'el' article for the noun. When preceding a feminine noun, 'a' stays as 'a' and the article is not replaced.
35. Miro a la televisión.
(I look at the TV.)
'televisión' is a feminine noun, so 'a' is used.
36. Escucho al profesor.
(I listen to the professor.)
'professor' is a masculine noun, so 'al' is used. Note the replacement of the 'el' article in this sentence.