Keeping the load factor (fullness) λ < 0.7 in a hash table:
A: means there usually are no collisions
B: keeps the number of collisions fairly small on average
C: wastes between 1 / 3 and 1 / 2 the table space
D: requires use of quadratic probing
E: B and C
Answer: E
With λ < 0.7 there will be some collisions
(about 1 on average), but this can be considered to be constant-time.
Keeping the table less than 0.7 full means we are wasting 0.3 of the
space at least, basically between 1 / 3 and 1 / 2.