Survey Observation of CH$_3$NH$_2$ and Its Formation Process
  We present the observational result of a glycine precursor, methylamine
(CH$_3$NH$_2$), together with methanol (CH$_3$OH) and methanimine (CH$_2$NH)
towards high-mass star-forming regions, NGC6334I, G10.47+0.03, G31.41+0.3, and
W51~e1/e2 using ALMA. The molecular abundances toward these sources were
derived using the rotational diagram method and compared with our
state-of-the-art chemical model. We found that the observed ratio of
"CH$_3$NH$_2$/CH$_3$OH" is in between 0.11 and 2.2. We also found that the
observed "CH$_3$NH$_2$/CH$_3$OH" ratio agrees well with our chemical model by
considering the formation of CH$_3$NH$_2$ on the grain surface via
hydrogenation process to HCN. This result clearly shows the importance of
hydrogenation processes to form CH$_3$NH$_2$. NGC63343I MM3, where CH$_3$NH$_2$
was not detected in this study and showed "CH$_3$NH$_2$/CH$_3$OH" ratio of less
than 0.02, is clearly distinguished from the other cores.
