Jean Baptiste Lamarck:

A. was one of the first scientists to propose that species evolve over time.
B. developed a widely accepted theory of evolution.
C. determined that Earth must be far older than most people believed.
D. said that famine and disease keep populations in check by killing off their weakest members.

Explanation:

According to Jean Baptiste Lamarck, fossils are the direct evidence of evolution and nucleotide sequence is the direct evidence of molecular evolution

He also explained about the use and disuse of organs, the organs which are used in priority will develop and the organs which are not used by priority will disintegrate

Lamarck said that vestigial organs in different organs is the direct evidence of use and disuse of organs  

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds