Run-on sentence. The sculptor liked a particular clay, he found it was very malleable.
This is a run-on sentence because there is an independent clause before the comma and an independent clause after the comma. A comma is not enough punctuation to create a compound sentence (combining two independent clause into one sentence). The comma needs to be a semicolon or there should be a conjunction after the comma.
Redundancy. The art class was amusing. The art class was challenging.
Redundancy is when something is repeated when it doesn't need to be because the repetition is not being used for effect. In these sentences "The art class was" is redundant. They should be revised to say "The art class was amusing and challenging."
Incorrect adjective or adverb usage. That photographer takes real good photos.
The incorrect usage in this sentence is "real". The word "real" is describing "good" which is an adjective. Adverbs describe adjectives not adjectives. It should be in the adverb form: really.
Inconsistent verb tense. The goalie reaches up and caught the ball.
In the sentence the first verbs "reaches" is written in present tense. The second verb "caught" is in past tense. Since they are two different tenses for the same subject, they have inconsistent verb tense.
Missing dialogue punctuation. Where are we going on vacation this year? I asked my mom.
In this sentence, the mother is asking a question. The question should be set off by quotation marks to clearly show what she said.
Incorrect pronoun case. Him and Andrea will be starring in the school play.
A pronoun is a word that takes the place of a noun. In this sentence the pronoun "him" is an object pronoun which means it receives the action rather than does the action. In the sentence "him" needs to be changed to "he" because he is a subject pronoun that does the action.