Which of these is considered a visual sign of potential chemical hazards?

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)?

Instruction active describing list features which statements accurately describe the features of word that are used to create lists? check all that apply. the tab key can be used to create a sublist. the enter key can be used to add an item to a list. the numbering feature allows for the use of letters in a list. the numbering feature can change the numbers to bullets in a list. the multilevel list feature provides options for different levels in a list.

An environmental protection agency study of 12 automobiles revealed a correlation of 0.47 between engine size and emissions. at 0.01 significance level, can we conclude that there is a positive association between the variables? what is the p value? interpret.