When you press your remote control you can see nothing coming from it. however, cameras on certain cell phones can photograph a small circular beam. what is the best explanation for this?

The answer is D (Remote controls often use infrared light to transmit information. This cannot be seen but can be picked up by some cameras.) I have had this question before.

thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.