Agroup of students went on a forest trail as part of their project activity. they were given a task of calculating the npp of a particular forest area they chose. they measured the gpp and the r values for that area as 1987 c/m2/day and 1674 c/m2/day, respectively. what is the npp of the area that these students selected?

It's C. 313 C/m^2/day.

Explanation:

NPP=GPP-R so 1987-1674=313

Unfortunately, this is a project. This site is for answers, which people explain what an answer is and why it's correct, which is legal. If one were to do this project for you, and you submitted it, even if you changed a couple of things, this would be plagiarism in an extreme form, which is illegal. You MUST do this on your own. 

I, however, will clarify what you need to do to make it simpler. You have a character who is exposed to thermal energy (heat energy, most thermal energy comes from the sun)

The thermal energy causes the character to change states, from a solid to a liquid, then to a gas.

Your character, obviously, should be made of a form of water. Water can exist in all three forms: Solids=Ice, Liquid=Any form of liquid water, Gas=Water Vapor, clouds, etc.

Now, since you have to start as a solid, your character needs to be made of Ice. The heat energy will first turn your character into a puddle of water, a liquid. Then, when enough heat energy is applied, your character, now a puddle of water, will transform into water vapor. This will go into the air and become a cloud. The cloud will release the water it's stored given enough time, and this will fall back down as rain, and then your character can magically become a solid again if you put it under correct conditions and temperatures. 

Part 1: Give your character a superhero name or something, Maybe Sub-Zero, Ive-Wave, Ice-Cube (the irony),  corny things like that. Give it an introduction, meaning explain the background of the character. Your character, should you heed my advice, is made of Ice, so state that.

Part 2: The source of thermal energy can be the sun, if you want. If you want something more dramatic, say a fire, which produces light and heat energy. Conduction vs Convection vs radiation will differ depending on what you choose. I recommend this site if you are unsure: 
http://coolcosmos.ipac.caltech.edu/cosmic_classroom/light_lessons/thermal/transfer.html

Part 3: Provide a detailed DESCRIPTION (Diagrams are more work, and you are more open to error) of how the particle transformation went to solid to a liquid. Solids are solid because their particles are SO packed together. When a solid becomes a liquid, those particles are free to move around freely and loosely. 

Part 4: Provide a DESCRIPTION of how the liquid went to a gas. When something is in liquid state, it's particles are loose and free, but still somewhat together, and are contained by whatever is holding the liquid, this is what keeps even a single drop of water together. When it becomes a gas, those particles go EVERYWHERE and have no limits as of to where. This makes the water untouchable and unable to be seen, as it is now water vapor.

Nobody can do this project for you without you getting into serious trouble because trust me: your teacher WILL find out.
But I just gave you step by step information on HOW to do this project precisely, and still customize it for yourself.

~Hope this helps m8