During the development of a tree, the lower limbs often die, but may remain attached for a time, sometimes years. Subsequent layers of growth of the attaching stem are no longer intimately joined with the dead limb, but are grown around it. Hence, dead branches produce knots which are not attached, and likely to drop out after the tree has been sawn into boards.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Rather than being joined to the limb that died, where do subsequent layers grow?
Ah, so.. around it

Although the advance in the Arakan had been halted to release troops and aircraft for the Battle of Imphal, the Americans and Chinese had continued to advance in northern Burma, aided by the Chindits operating against the Japanese lines of communication. In the middle of 1944 the Chinese Expeditionary Force invaded northern Burma from Yunnan province. They captured a fortified position at Mount Song. By the time campaigning ceased during the monsoon rains, the NCAC had secured a vital airfield at Myitkyina (August 1944), which eased the problems of air resupply from India to China over "The Hump".
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): When did the Chinese invade northern Burma?
Ah, so.. middle of 1944

Gram-positive bacteria possess a thick cell wall containing many layers of peptidoglycan and teichoic acids. In contrast, gram-negative bacteria have a relatively thin cell wall consisting of a few layers of peptidoglycan surrounded by a second lipid membrane containing lipopolysaccharides and lipoproteins. Lipopolysaccharides, also called endotoxins, are composed of polysaccharides and lipid A that is responsible for much of the toxicity of gram-negative bacteria. Most bacteria have the gram-negative cell wall, and only the Firmicutes and Actinobacteria have the alternative gram-positive arrangement. These two groups were previously known as the low G+C and high G+C Gram-positive bacteria, respectively. These differences in structure can produce differences in antibiotic susceptibility; for instance, vancomycin can kill only gram-positive bacteria and is ineffective against gram-negative pathogens, such as Haemophilus influenzae or Pseudomonas aeruginosa. If the bacterial cell wall is entirely removed, it is called a protoplast, whereas if it is partially removed, it is called a spheroplast. -Lactam antibiotics, such as penicillin, inhibit the formation of peptidoglycan cross-links in the bacterial cell wall. The enzyme lysozyme, found in human tears, also digests the cell wall of bacteria and is the body's main defense against eye infections.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What can be endotoxins called?
Ah, so..
Lipopolysaccharides