Answer:
जनसंख्या घनत्व भनेको कुनै निश्चित क्षेत्रमा कति मानिस हुन्छन्.
Stress is positive or negative depending on the circumstances and a negative reaction to outside influences.<span />
13: saliva (option B)
14: Tongue
15: esophagus
16: stomach
17: enzymes
18: chyme
19: small intestine
