TOEFL Reading Practice Test #6

According to paragraph 1, a rattlesnake strikes only at warm-blooded prey, and when the prey is dead and at room temperature, the snake will not strike. The passage also explains that even a blindfolded snake will strike at a warm object, like a dead rat, if it is warmer than the surroundings, showing that temperature, not sight, movement, or chemical odors, guides the strike.

The author mentions the "cloth-wrapped electric bulb" to demonstrate that the snake is not using its sense of smell to locate prey. Despite the lack of smell from the electric bulb, the blindfolded snake still strikes at it, which suggests that the snake's strike is based on detecting heat, not odor. This eliminates the possibility that the snake relies on smell to find its prey.

Option B most accurately reflects the original sentence, explaining that objects with a different temperature from the surroundings cause a noticeable change in nerve activity when they enter the receptive field near the snake’s head. Other choices either add incorrect information or misinterpret the original meaning.

"Deformation" refers to a change in the shape or structure of something, often due to external forces. "Distortion" is the closest in meaning as it implies a change or alteration from the original form. "Alteration" is somewhat similar but less specific, while "creation" and "arrangement" do not fit the meaning of "deformation."

In paragraph 3, it is mentioned that a cut in the membrane of the pit organ does not result in a loss of responsiveness, which suggests that the ability of a rattlesnake to detect warm objects is not impaired if the membrane is damaged. This means that even when the pit organ's membrane is compromised, the rattlesnake can still detect temperature changes and locate warm objects, which supports the idea that the pit organs are involved in sensing infrared radiation rather than relying on pressure changes.

In paragraph 4, it is explained that the infrared radiation emitted by a mammalian body has low quantum energy, which makes any photochemical effect on pigments in the pit organs highly unlikely. This indicates that a photochemical explanation, which would involve light-sensitive pigments similar to those in the eyes, is improbable because the energy level of infrared radiation is insufficient to affect such pigments.

"Substantially" means to a large extent or degree, which aligns closely with "significantly." The other options—reliably, undoubtedly, and frequently—do not convey the same sense of a major or notable impact.

The separation of nerves in the right and left eyes and pit organs does not support the idea of stereoscopic perception. In fact, it is the coordination and interpretation of input from both pit organs and eyes that supports the idea of stereoscopic perception. The other options discuss how the sensory and neural processes related to the pit organs and the brain's response align with the concept of stereoscopic vision.

This placement is ideal because the sentence provides general context about how some animals have specialized organs for detecting infrared radiation, which supports understanding the specific function of pit organs in snakes. By placing it after the first sentence, it sets up the discussion on how these specialized organs work, which is relevant to the passage’s focus on the function of pit organs in detecting infrared radiation.

Explanation:

• A) This option summarizes the primary function of the pit organs, which is to locate warm-blooded prey.
• E) This option aligns with the passage’s discussion on the sensitivity of pit organs to infrared radiation.
• F) This option reflects the passage's conclusion about how the pit organs contribute to the precision of prey location, including stereoscopic perception.

B) and D) do not fit well with the main ideas. B) mentions a variety of stimuli not strongly emphasized in the passage, and D) is a minor detail not central to the passage's main points. C), while relevant, is less directly tied to the core idea of infrared sensitivity than E).