The person who goes into space is called an Astronaut.

An astronaut is a highly trained professional who travels into space to conduct scientific research, explore new frontiers, and perform various tasks related to space exploration. Let's delve into the details of why the correct answer for this question is option 'C'.

Explanation:

Astronaut:
- An astronaut is an individual who is trained to travel and work in space.
- They are part of space missions and expeditions, and their primary role is to carry out scientific experiments, operate spacecraft and space stations, and contribute to the advancement of space exploration.
- Astronauts undergo rigorous training for many years to prepare themselves physically, mentally, and technically for the challenges they will face in space.

Architect:
- An architect is a professional who designs buildings and structures.
- Their work involves planning, designing, and overseeing the construction of various architectural projects.
- Architects are not directly involved in space exploration or travel.

Geologist:
- A geologist is a scientist who studies the Earth's solid materials, such as rocks, minerals, and the processes that shape the Earth.
- They analyze the composition, structure, and history of the Earth's crust to understand its geological evolution.
- Geologists primarily focus on studying the Earth and its features rather than space exploration.

Ornithologist:
- An ornithologist is a scientist who specializes in the study of birds.
- They observe and analyze various aspects of birds, including their behavior, habitats, migration patterns, and physiology.
- Ornithologists do not have any direct involvement in space exploration or travel.

Therefore, based on the given options, the correct answer is 'C' - Astronaut, as this is the only option that accurately describes a person who goes into space and is involved in space missions and expeditions.