This part of the electromagnetic spectrum produces heat and with special equipment can locate people at night

infrared waves
microwaves
x-rays
gamma waves

Option A, Infrared waves

Explanation:

Infrared waves

Infrared radiations (IR) are the radiation that lies in the wave length range of 700 nanometers to 1 millimeter. However its frequency is the shortest

The wavelength of IR is higher than the visible light and hence it is invisible but it can be sensed as heat due to which they are used in thermal imaging and night vision equipment.  

Therefore, option A is correct.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

preservation because he preserves part of the land and preserves means save

explanation: