Answer:
Because the trophozoites are unable to survive outside a host.
Explanation:
The term infectious is used for a disease or microorganism that can be transmitted from one organism to the other organism through the environment. If we look at the two forms of Giardia, we find that out of the two forms viz. cysts and trophozoites, only the cysts of Giardia have the ability to remain alive in the environment outside the host and thus they are able to be transmitted to the other organisms. On the other hand trophozoites are not able to survive in outside environment so there is no chance of transmission of trophozoites.
Acceleration of a body is defined as rate of chance in velocity with respect to time and its S.I. Units are 
/ or 
Magnitude of average acceleration of a body = (final speed - initial speed)/time interval = 
where, final speed =v= 11 m/s; initial speed = u = 6 m/s; and time interval = t = 3 s
Hence acceleration = 
= 
= 
"Different substances sometimes have the same chemical formula, such as glucose and fructose, but they have different components so they act differently."
Xylem is a very useful tissue in plants used for transportation of water from roots of a plant to its upper part for its proper growth
Answer:
Seismographs record seismic waves. They contain a weight and a pen attached to a spring. The seismograph is bolted to the ground so during an earthquake it moves with the ground, whilst the weight and pen remain still. The pen moves across a rotating paper roll recording the seismic waves.
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