Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: PM$_{2.5}$ as a major predictor of COVID-19 basic reproduction number in
  the USA
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
3
The categories of this paper are: physics
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
12
The categories of this paper are: nucl-th
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph