Final answer:
As subject tissue thickness increases, absorption increases, and transmission decreases, while beam attenuation also increases, not decreases.
Step-by-step explanation:
When the subject tissue thickness increases, beam attenuation increases, which means absorption of the beam also increases. Consequently, the transmission through the tissue decreases because more of the beam energy is being absorbed. Therefore, the correct answer to the question is 2 and 3 only, as subject tissue thickness does not cause a decrease in beam attenuation; rather, it causes an increase.