Regulation and maintenance of constant internal conditions in an organism
a. hemoglobin
b. photosynthesis
c. hypothesis
d. homeostasis

The answer is D homeostasis. For A, hemoglobin is a protein exists in blood and can bring oxygen. For B, photosynthesis is a process of converting CO2 to glucose using the energy of light. It occurs in chloroplast. For C, hypothesis means suppose.

Primary succession, type of ecological succession (the evolution of a biological community's ecological structure) in which plants and animals first colonize a barren, lifeless habitat. Primary succession occurs when new land is formed or bare rock is exposed, providing a habitat that can be colonized for the first time. For example, primary succession may take place following the eruption of volcanoes, such as those on the Big Island of Hawaii. As lava flows into the ocean, new rock is formed.

Explanation: