What should come in place of the question mark (?) in the given series?

38 ,37 ,40, 39, 42, ?

Choose the correct alternatives that will continue the same pattern and replace the question mark (?), in the following number series.
99, 33, 36, 12, 15, 5, ?

Which of the following numbers will replace the question mark (?) in the given series?
2548, 3150, ?, 4624, 5508​

What should come in place of the question mark (?) in the following series?
2, 6, 12, 20, ?

What should come in place of the question mark (?) in the given series?
91, 102, 119, 142, 171, ?

What should come in place of the question mark (?) in the given series?
108, 122, 139, 159, 182, 208, ?

Select the number from among the given options that can replace the question mark (?) in the following series.
44, 55, 68, 83, 100, ?