Which of the following best characterizes a covalent bond?
a. occurs when elements have opposite electrical charge
b. occurs when elements have very different electronegativity values
c. occurs when atoms have similar tendencies to attract electrons and share electrons between them
d. occurs when atoms are of the same size

Scientists are conducting a study on the effectiveness of a new drug on memory loss. they are giving some of the test subjects the new drug to find out if it improves their long-term memory. which are possible limitations of this study? check all that apply. a) test subjects may want to participate in additional experiments. b) test subjects may think they should be paid more. c) test subjects may get bored and want to quit early. d) test subjects may have to travel during the experiment. e) test subjects may have full-time jobs. this is multiple choice. you for the !