What is true about trna's: o they vary widely in size o they can covalently bond to more than one type of amino acid 0 they do not have any stem loop structures o they contain an anticodon triplet that recognizes a mrna codon 0 there are exactly 20 different trna's

Option (3).

Explanation:

Transfer RNA or t RNA's is one of the type of the RNA molecule necessary for the synthesis of protein translation. This RNA works as a adaptor molecule and contains 70 to 90 nucleotide in length.

Transfer RNA contains an anti codon loop. This anti codon loop has the ability to recognize an mRNA codon and result in the formation of protein product.

Thus, the correct answer is option (3).

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.