You hear: mi novio siempre me compra flores para nuestro aniversario. you write: flores en la categoría plantas plantas flores animales

Considering that there are three options: a) plants; b) flowers; c) animals, the correct answer is option b) flowers.

Explanation:

Animals are living organisms that grow, live, have a sexually reproduction (different from plants) and can move freely as they are not depended of the nutrients of the ground and on the other hand they consume organic material formed by the plants or other animals. Therefore option c) animals is not correct because a flower is not a living organism that reproduces sexually and moves freely.

Plants are organic beings that grow, live and reproduce. They obtain energy from the Sun light by the process called photosynthesis. Even if they cannot move, they grow roots to take nutrients from the ground. Plant Etymology comes from Latin word "plantae" that means: "sprout", and  its semantics says: something establish in the ground. So, anything that grows from the ground and makes photosynthesis could be categorized as PLANT.

Flowers are the bloom of the plants called angiosperms, that are the ones that erect a structure that allows the plant to reproduce (the well-known flower), therefore flowers normally are colorful and striking to facilite attraction and subsequent reproduction.

Now, option a) plants could be right, because the general category of flowers is plants, but it is not specific as option b) flowers, that refers directly to the bloom of the plant (not the plant itself), thus the correct answer is option b) flowers, as the boyfriend is giving only the bloom to her girlfriend and not the whole plant.