Question

based on the observation of a puddle on the sidewalk, which of the following is a logical inference?
the sidewalk is made of concrete.
the sun will come out soon.
it must have rained recently.
someone spilled a bucket of water.
based on the observation that a certain bacteria grows faster in warmer temperatures, which of the following is a testable hypothesis?
bacteria growth is affected by temperature.
different types of bacteria grow at different rates.
warmer temperatures cause faster bacteria growth.
if the temperature is increased, then the rate of bacterial growth will increase.
a scientist observes that a specific bird species builds its nest with a particular type of grass. which of the following is a testable hypothesis?
this bird species prefers this type of grass for its nests.
different bird species use different materials for their nests.
the availability of this specific grass influences the nesting behavior of this bird species.
birds build nests.

Explanation:

• For the first question: Observing a puddle, the most logical inference is that it rained recently as rain is a common cause of puddles. The other options are either direct observations (sidewalk material) or less likely assumptions (sun coming out soon, someone spilling water which is more specific and less common as a cause compared to rain).
• For the second question: A testable hypothesis should be in an “if - then” format that clearly states the relationship between the independent variable (temperature) and the dependent variable (bacterial growth). “If the temperature is increased, then the rate of bacterial growth will increase” is testable as you can manipulate temperature (independent variable) and measure bacterial growth (dependent variable). The other options are either too general (bacteria growth is affected by temperature) or not focused on the observed relationship (different types of bacteria grow at different rates).
• For the third question: “The availability of this specific grass influences the nesting behavior of this bird species” is a testable hypothesis. You can manipulate the availability of the grass (independent variable) and observe the nesting behavior (dependent variable). The other options are either observations (this bird species prefers this type of grass for its nests - more of a description), about other bird species (different bird species use different materials for their nests - not focused on the observed bird - grass relationship), or too general (birds build nests).

Answer:

1. It must have rained recently.
2. If the temperature is increased, then the rate of bacterial growth will increase.
3. The availability of this specific grass influences the nesting behavior of this bird species.