$4.$ Give regular expressions that describe the languages. In all parts, the alphabet is $\{0,1\}.(20$ points$)$

For the correct format, please check our examples in slides and use the following symbols: $0,1,,*,(),$ U$.$

Other formats like this $^1(0+1)*$$ will not be graded. PLS PAY ATTENTION TO THIS INSTRUCTION.

a$.\{$w$|$ w starts with $0$ and has an odd length$\}$

b$.\{$w$|$ w starts with $1$ and has an even length$\}$

c$.\{$w$|$ w contains at least two $0$s$\}$

d$.\{$w$|$ w contains at most one $1\}$