Final answer:
Streptococcus pneumoniae matches the description of small, gram-positive lancet-shaped cells arranged in pairs and short chains. It causes pneumonia and other respiratory infections.
Step-by-step explanation:
The small, gram-positive lancet-shaped cells arranged in pairs and short chains match the description of Streptococcus pneumoniae (S. pneumoniae). S. pneumoniae is a bacterium that causes pneumonia and other respiratory infections. It can also cause other diseases such as meningitis, septicemia, osteomyelitis, and endocarditis, especially in vulnerable populations.