Which of these statements are true?

a. both high- and low-pressure systems lead to rain.
b. low-pressure systems lead to rain.
c. high-pressure systems lead to rain.
d. neither high- nor low-pressure systems lead to rain

According to valence bond theory, which orbitals overlap in the formation of the bond in hf according to valence bond theory, which orbitals overlap in the formation of the bond in hf 2s on h and 2p on f 1s on h and 2s on f 1s on h and 1p on f 1s on h and 2p on f 1s on h and 3p on f