what are the regular expersions of these?

a {w | w starts with 0 and has odd length, or starts with 1 and has even length}

b. {w | every odd position of w is 1}

c {w | w contain at least two 0s and at most one 1}

d {w | w contains exactly one zero and two ones}

e {w | the length of x is at most 3}

f {w | every 0 in w must be followed by at least one 1}