x(t) is nonzero only for $T_x$<t<${T}'x$ , and similarly, y(t) is nonzero only for $T_y$<t<${T}'y$. Let
z(t)  be convolution of x(t) and y(t). Which one of the following statements is TRUE?

1. z(t) can be nonzero over an unbounded interval.
2. z(t) is nonzero for t<($T_x$+$T_y$)
3. z(t) is zero outside of $T_x$+$T_y$<t<${T}'_x+{T}'_y$
4. z(t) is nonzero for t>${T}'_x+{T}'_y$

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