This could be caused by one of three things: (1) Your tree is growing more leaves than it can support, (2) pests and diseases infect the leaves, or (3) your tree might be getting too much or too little water.
I think it is C. <span>Obstacles make us stronger, because a theme is the central idea of the story but D also kinda sounds like a theme.
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I agree strongly because it makes so mych sense
