Q: Given a passage and a question, find the answer to the question based on the passage. The answer should consist of only one word that lies in the span of only one of the sentences in the passage.
Paragraph: Acer / esr / is a genus of trees or shrubs commonly known as maple . The genus is placed in the Sapindaceae family . There are approximately 128 species , most of which are native to Asia , with a number also appearing in Europe , northern Africa , and North America . Only one species , Acer laurinum , extends to the Southern Hemisphere . The type species of the genus is the sycamore maple , Acer pseudoplatanus , the most common maple species in Europe .
Question: how many kinds of maple trees are there

A:
128