Chose extended regular expression for given pattern in question 7) to 9): Question 7 (3 points) Valid variable names contain letters, digits or underscores, but must begin with a letter. E.g. AName, T, var_1, test1, test_1 are all valid variable names None of above O [a-zA-Z][a-zA-Z0-9]+ [a-zA-Z] [a-zA-Z0-9_1* O [a-zA-Z_][a-zA-Z0-9_]+ [a-zA-Z_][a-zA-Z0-9_1" Question 8 (3 points) Positive numbers greater than or equal to 40 but less than 60. E.g. 43, 45, 40, 59 are matched positive numbers O [4-6][0-9] [456][1-9] None of above O [4-5][0-9] O [4-6][2] Question 9 (3 points) Words that start with "ba" and not contain 'o'. E.g. banana, balance, barrier [^ba][^o]* O None of above Aba[^o]* ba[^o]*^ ba(o)*