Hi, so I’m a junior in high school and I have all A’s right now and 1 C and I feel like I can only get a C by the end of the year 
Comparing to my freshmen and sophomore year my gpa increased A LOT and I decided that I’m majoring in business/accounting and minoring in music. I understand the basic concepts in my class but the tests (from last year’s students) said were harder than the AP exam. I studied extremely hard for four days for that class and ended up a C on the test while others who study the day before gets a higher grade than me…Science isn’t my strongest subject and I’m trying to fix it but it’s not working out how I planned. So my dream school is UMD College Park… Will that C keep me from applying and actually getting into that school? Next year I’m only taking one ap class and rest honors and gt while taking two more classes outside of school at a community college to get my dual credits.
I don’t know how you can just give up like that and decide all these months in advance that you are going to “only get a C by the end of the year.” That’s not the right attitude. You will have to take lots of classes in college that are not your “strongest subject” and you can’t just decide to make low grades because of it. Figure out how to make at least a B in that class. Buy an AP Environmental Science study book and use it. Study with one of the students who makes As easily and learn how it’s done. Meet with the teacher to figure out what concepts you are missing and how to improve. Look at your syllabus and how the grade is determined, and see what areas you can improve. Ask for extra credit work. You should be determined to figure this out and improve!
Let me answer your questions though. No, one C should not be the deciding factor for whether you get into UMD College Park or not. They will look at everything – the difficulty level of your curriculum, your grades, your test scores, your leadership and honors and awards, etc. Whatever they ask for in the application is what they will look at, not just your AP Environmental Science grade. You can also try to counter the grade by making a 3 or higher on the AP exam.