The correct answer is letter B: A streak test.
A covalent bond means shared electrons between atoms. This is similar to kids sharing markers because the markers (electrons) are being shared between the kids (atoms). Covalent bonds are different than this metaphor because 1) the electrons are constantly moving about while the kids can steal and keep the markers and 2) the electrons and atoms are physically smaller
Calculate the H positive from the pH equation: pH equals -log (H positive). This would be 10 to the -6.49. Let's call the acid HA. To calculate Ka in this equation, Ka equals H positive times A- over HA. HA is going to be the 0 0121. So, Ka=(10^-6.49)^2/0.0121. This equals 1.05*10^-13/0.0121. Ka then equals 8.65*10^-12.
Apsidal precession—The major axis of Moon's elliptical orbit rotates by one complete revolution once every 8.85 years in the same direction as the Moon's rotation itself.