Help me with this in the picture below

Which statement is true about a number and its additive inverse? a. their product is always one. b. their sum is always one. c. they are always reciprocals of each other. d. their sum is always zero.

Which expression is equivalent to -12(3x-3/4)

Which of the following is the major negative aspect of crossover designs for research studies? a. prohibitive cost b. residual effects c-subject drepout d. incomplete randomization e. large sample size required