[It works much better to write expressions using ~(x) since it's hard get the over-bars aligned across all browsers.]

The truth table gives the canonical expression

(a)(~b)(~sel) + a(b)(~sel) + (~a)(b)(~sel) + (a)(b)(sel)

Putting these terms into a k-map gives

The minimum required terms are (a)(~sel) and (b)(sel).

A common mistake when learning k-maps is not to recognize terms that wrap around the edges as in (a)(~sel). Also note that in 4x4 k-maps, the 4 corners are a term.

An easy way to convert expressions to gates is to rewrite them in "function" form. For example

(a)(b)(~c)+d

is

OR (AND (AND (a,b), NOT (c)), d)

--Mark