1. which of the following is always single-stranded?
a. messenger rna (mrna)
b. double-stranded rna (dsrna)
c. dna
d. dna and rna
(obviously its not b.)
2. which of the following is a difference between dna and rna?
a. most types of rna are double-stranded
b. rna contains lipids
c. they have different sugars
d. rna has thymine
3. which of the following bases are found in rna but not in dna?
a. uracil
b. guanine
c. adenine
d. cytosine
i'm pretty sure 3 is a. but i want to be sure.

A - mRNA

C - they have different sugars.

A - uracil

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explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.

answer; i believe that the correct answer is(d) nondisjunction during meiosis;