When it comes to the $29\mathrm{.}5-$year bond and the $30-$year bond, which is favored in being bought and being sold and Why?

$29\mathrm{.}5-$year bond will be bought to reimvest the profit and buy the $30-$year bond in anocher contract. The $30-$year bond will be cheaper than the $29\mathrm{.}5-$year bond.

$29\mathrm{.}5-$year bond are usually sold short because it is not as new as the $30-$year bond so buyers are not interested; they will buy the $30-$year bond due to popularity.

$20-$year t$-$bohd futures are terally teld thort becance it it new and overpriced, they will buy the $29\mathrm{.}5$ year bond in another market and hope the prices will converge for profit.

Both bonds will be bought then later reinvested in the futures market for profit.