Final answer:
The first noticeable signs of oxygen deficiency typically include dizziness, impaired vision, and giddiness, which can be associated with hypoxia and anemia.
Step-by-step explanation:
The first noticeable signs of oxygen deficiency are often related to the body's increased need for oxygen that cannot be met due to a variety of reasons such as high altitudes, anemia, or carbon monoxide poisoning. Given the options provided, the most accurate answer to what the first noticeable signs of oxygen deficiency are would be dizziness, impaired vision, and giddiness. These symptoms can be related to hypoxia, a condition where there is insufficient oxygen to meet physiological needs and can cause various symptoms including fatigue, headaches, confusion, and symptoms similar to acute mountain sickness (AMS) including disorientation, fatigue, and nausea. Additionally, anemia, which is a decrease in the number of red blood cells, can cause weakness, tiredness, and shortness of breath among other symptoms due to the reduced oxygen-carrying capacity of the blood.