In quiet breathing (a) inspiration is passive and expiration involves muscular contractions. (b) inspiration and expiration involve muscular contractions.(c) inspiration and expiration are both passive processes. (d) inspiration involves muscular contractions and expiration is passive. (e) none of these.

In quiet breathing inspiration involves muscular contractions and expiration is passive.

Explanation:

Respiration process involves two different stages, inspiration - inhalation- and expiration - exhalation-.

During inspiration, the diaphragm contracts and goes down, while intercostal muscles also contract and go up. These actions enhance the size of the thoracic box and reduce internal pressure. As a result, air flows in and fills the lungs.

During expiration, the diaphragm relaxes and the volume of the thoracic box diminishes, which causes the pressure inside to increase. In consequence, the lungs contract and the air is expulsed outside.  

weathering - colorado river carves land in arizona to form the grand canyon. cracks form in a sandstone wall surrounding a house. a marble statue near the science museum is changing color due to rainfall

erosion - after a rainstorm, soil and rock piees litter the roadways. the sand dunes in the sahara desert are changing shape.

here's your answer.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.