What is a characteristic of a magnetic reed switch? Select one:
a. Switch contacts that are not enclosed
b. Bigger size than mechanical switches
C. High sensitivity to magnetic fields
d. Very high voltage flows through contacts

Idon understand these and need some ! ?

When running anti-virus software , what could be a reason where recipitent is not guaranteed that data being streamed will not get interrupted?

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)?