4.
颗粒物局貌。A：C1颗粒物局貌(×10, 000)；B：K7颗粒物局貌(×10, 000)；C：M30颗粒物局貌(×10, 000)。
Particle board looks. A: C1 particle board looks; B: K7 particle board looks; C: M30 particle board looks.
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