Adaptations

Desert lizards lack the physiological ability that mammals have to deal with the high temperatures of their habitat.
They manage to keep their body temperature fairly constant by behavioural means.
They bask in the sun and absorb heat when their body temperature drops below the comfort zone, so (c) is correct.
They move into shade, or burrow into the soil, when the ambient temperature starts increasing, so (a) is correct.
They cannot lose heat rapidly by a physiological mechanism such as sweating, so (b) is wrong; a thick layer of fat (blubber) for insulation is an adaptation of aquatic mammals of cold seas such as seals, so (d) is wrong.
Hence the correct pair is (a) and (c).

At high altitude the atmospheric pressure is low, so the body does not get enough oxygen and the person may suffer from altitude sickness (nausea, fatigue, heart palpitations).
The body gradually gets acclimatised and compensates for the low oxygen availability by: increasing red blood cell production, decreasing the binding affinity of haemoglobin, and increasing the breathing rate.
So (b) and (c) occur.
The size of red blood cells and the thrombocyte (platelet) count are not part of this response, so (a) and (d) do not occur.
Hence the changes are (b) and (c).