Construct tangent ZY passing through T and is tangential to C1 & C2
<QTZ=<QBT (angle between tangent and chord is equal to angle subtended by that chord in the alternate segment)
Similarly <YTP = <TAP
<TAP=<QBT (alternate angles on parallel lines are equal QBllPA)
Therefore <QTZ=<YTP...
+1 It's valid because you prove they're equal angles and THEN you state well since they're equal, they must be vertically opposite. Hence straight line.
Speed is scalar and does not have direction as you pointed out above. Your interpretation is not valid as acceleration can only be worked with velocity and then converted to speed (valid due to this being linear motion).
10 is definitely D. By Newton's second law F=ma acceleration is interchangeable with force. If you act a force in a direction that is opposite to the currently velocity of a particle it will slow down. ie. If your chair is rolling forwards and someone pushes (accelerates) you in the opposite...