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Which of the following curves is smooth in the interval $(-\infty, \infty)$?

$\sin t {\bf i}+(t^2-\pi t) {\bf j}$

$e^t{\bf i}+t^2{\bf j}$

$t{\bf i}+|t|{\bf j}$

$(t^2-1) {\bf i}+(t^3-0.75t){\bf j}$

$\sin t {\bf i}+\sin^2 t {\bf j}$