The parametric curve given by

$x=2t+lnt$ and $y=2t-lnt$

is

a$.$

concave downward when $t>\frac{1}{2}t>\frac{1}{2}t>0t>00$ and concave downward when $t>\frac{1}{2}.$

$d.$ concave upward when $t>0.$

$e.$ concave downward when $t>0\mathrm{.}0$ and concave upward when $t>\frac{1}{2}$

concave upward when $0$ and concave downward when $t>\frac{1}{2}.$

$d.$ concave upward when $t>0.$

$e.$ concave downward when $t>0\mathrm{.}0$

$b.$ concave downward when $0$ and concave upward when $t>\frac{1}{2}$

concave upward when $0$ and concave downward when $t>\frac{1}{2}.$

$d.$ concave upward when $t>0.$

$e.$ concave downward when $t>0.$