Is the statement "$A$ particle can have zero speed but non-zero velocity" true or false? Explain.

$A$ boy walks to his school at a distance of $6\, km$ with a constant speed of $2.5\, km/h$ and walks back with a constant speed of $4\, km/h$. His average speed for the round trip,expressed in $km/h$,is:

$A$ body moves with velocities $v$,$2v$,and $3v$ in the first,second,and third one-third distances of the path traveled,respectively. Its average speed is:

$A$ particle travels half of the distance of a straight journey with a speed $6 \,m/s$. The remaining part of the distance is covered with speed $2 \,m/s$ for half of the time of the remaining journey and with speed $4 \,m/s$ for the other half of the time. The average speed of the particle is ....... $m/s$.

$A$ body travelling along a straight line path travels the first half of the distance with a velocity of $7 \,m/s$. During the travel time of the second half of the distance, the first half of the time is travelled with a velocity of $14 \,m/s$ and the second half of the time is travelled with a velocity of $21 \,m/s$. Then the average velocity of the body during the entire journey is: (in $\,m/s$)

Is it possible for a moving object to have a constant velocity and a changing speed?