Besides (r^2) and (s^2), which term appears in ( (r+s)^2 )?

Correct answer: (2rs)

The direct answer is D: the additional term is 2rs. Start with the identity \\(r+s\\)^2=r^2+2rs+s^2\\). The square means multiplying the whole expression by itself: \\(r+s\\)(r+s). Multiplying term by term gives \\(r^2+rs+sr+s^2\\). Since \\(rs=sr\\), the two middle terms combine to \\(2rs\\). Therefore the complete expansion contains r², 2rs and s². Option D is correct. Option A, -2rs, belongs to the middle term of \\(r-s\\)^2\\), not a plus square. Option B, rs, misses one of the two equal cross-products. Option C, -rs, has the wrong sign and also the wrong coefficient. The common mistake is to write only r²+s² and forget the cross terms. Cue: plus square means positive double product.