automata theory

The minimum possible number of states of a deterministic finite automaton that accepts the regular language L = {w1aw2 | w1, w2 ∈ {a, b}*, |w1| = 2, |w2| ≥ 3} is

Which one of the following regular expressions represents the language: the set of all binary strings having two consecutive $$0s$$ and two consecutive $$1s?$$

Which one of the following regular expressions over $$\left\{ {0,\,\,1} \right\}$$ denotes the set of all strings not containing $$100$$ as substring?