Is there a trick to remembering when something is masculine or feminine? I can't remember all of them.
There is no trick to the gender of the nouns, for the most part. It's straight memorization as far as I know.
Look at the noun, feminine nouns usually end in an e, so you know the adjectives will be feminine too. :
garçon means boy and is masculine (no e at the end) fille means girl and is feminine (notice the e at the end)
Les grands garçons (The big boys) Les grandes filles (The big girls)
Notice how you use the masculine version of big (grand) when talking about boys, and the feminine version (grande) when talking about girls.
I would be very careful with this "rule" : a noun ending by an 'e' is probably feminine... See un père, un frère, un crime, un sucre, un verbe, un livre and see also a lot of noun ending by -age and -isme : un orage, un ouvrage, un nuage, un mirage ; (BUT une image) un traumatisme, un parallélisme.
The only explanation I could possible have is that they want you to answer with what they teach you.Otherwise you could as well just try it without their help.
I say "les mots" one time and "des mots" another.... apparently they are both wrong.
The section that says words really needs to be updated you should be able to like search words from a certain topic like you could search food and the food words would pop up. Like seriously.