My father and I have already visited several states this month.On June 20, dad's friends Helena and Franco Garabis met us in Brownsville, Texas.

I had to capitalize all the errors in the above sentence but it still has one more that is capitalized and I'm not sure which one should be. It's either father, states or dad's.

Dad's should be capitalized.

To identify the error in the given sentence, let's break down the options:

1. Father: Normally, when referring to a person's father, "father" is not capitalized. However, if "Father" is being used as a proper noun or as a title, such as when addressing a religious figure, it would be capitalized. In this sentence, without further context, it is unlikely that "Father" should be capitalized.

2. States: Generally, common nouns like "states" are not capitalized unless they are used as part of a proper noun or a proper name. For example, if the sentence mentioned specific states like "New York" or "Texas," those would be capitalized. However, in the given sentence, "states" is used in a general sense, so it should not be capitalized.

3. Dad's: Possessive pronouns like "dad's" are typically not capitalized, unless they begin a sentence or are used as part of a title or proper name. For instance, if the sentence started with "Dad's friends," then "Dad's" would be capitalized. However, in the sentence provided, "dad's" is not at the beginning, and no other indications suggest it should be capitalized.

Based on the analysis above, none of the options (father, states, dad's) require capitalization. Hence, the sentence should be as follows:

"My father and I have already visited several states this month. On June 20, dad's friends Helena and Franco Garabis met us in Brownsville, Texas."