Final answer:
Yasir's scientific investigation is missing an actual experiment that tests the hypothesis. He should conduct a controlled experiment to measure sleep latency in different room colors.
Step-by-step explanation:
Yasir is trying to determine if there is a relationship between room color and sleep. He postulates that people fall asleep faster in rooms painted blue compared to those painted yellow. However, instead of conducting an experiment that tests the hypothesis, he merely asks people which color they prefer. The major element missing from his scientific investigation is a B. experiment that tests the hypothesis. To validate his hypothesis, Yasir should design an experiment with a control group and a variable group, where some participants sleep in blue rooms and others in yellow, then measure how quickly they fall asleep. Additionally, he should ensure that other variables are controlled so that the results solely reflect the impact of room color on sleep latency.