Three reasons why a valley flashing is a vulnerable area are:

The correct answer highlights three critical vulnerabilities associated with valley flashing, which is the area where two roof slopes meet, creating a trough that directs water runoff. Snow and ice accumulation is a key concern because, in colder climates, this build-up can lead to melting and refreezing cycles that may compromise the flashing's integrity. The mention of valleys having a lower slope is also significant because gentler slopes can lead to slower drainage, increasing the risk of water pooling, which can lead to leaks or water damage. Additionally, the susceptibility of valleys to stretching and buckling underscores the structural challenges posed by weather conditions, which can put stress on the flashing material and potentially lead to failure over time.

The focus on snow and ice, slope issues, and material strain in the correct choice reveals the complex interaction between environmental conditions and construction design, which is essential knowledge for home inspectors who need to assess roofing systems effectively.