Which option identifies why the hypothesis in the following scenario is an if then hypotheis? The following hypothesis is proposed for a study: skin cancer rates will decrease when sunscreen is applied.

The statement involves unrelated items.

The items in the statement are unaffected by each other.

The statement makes a conclusion.

The items in the statement have a cause-effect relationship.

Who is the first president to use social media as part of his campaign strategy

What is a distinguishing feature of today’s graphic application software?) graphic applications are used today on a variety of devices, including touch-screen kiosks and mobile phones.

Suppose there is a relation r(a, b, c) with a b+-tree index with search keys (a, b).1. what is the worst-case cost of finding records satisfying 10 < a < 50 using this index, in terms of the number of records n1, retrieved and the height h of the tree? 2. what is the worst-case cost of finding records satisfying 10 < a < 50 and 5 < b < 10 using this index, in terms of the number of records n2 that satisfy this selection, as well as n1 and h defined above? 3. under what conditions on n1 and n2, would the index be an efficient way of finding records satisfying the condition from part (2)?