  We present line and continuum observations (resolution ~0.3"-3.5") made with
the Atacama Large Millimeter/submillimeter Array (ALMA), Submillimeter Array,
and Very Large Array of a young O-type protostar W42-MME (mass: 19-4 Msun). The
ALMA 1.35 mm continuum map (resolution ~1") shows that W42-MME is embedded in
one of the cores (i.e., MM1) located within a thermally supercritical
filament-like feature (extent ~0.15 pc) containing three cores (mass ~1-4.4
Msun). Several dense/hot gas tracers are detected toward MM1, suggesting the
presence of a hot molecular core with the gas temperature of ~38-220~K. The
ALMA 865 micron continuum map (resolution ~0.3") reveals at least five
continuum sources/peaks ("A-E") within a dusty envelope (extent ~9000 AU)
toward MM1, where shocks are traced in the SiO(8-7) emission. The source "A"
associated with W42-MME is seen almost at the center of the dusty envelope, and
is surrounded by other continuum peaks. The ALMA CO(3-2) and SiO(8-7) line
observations show the bipolar outflow extended below 10000 AU, which is driven
by the source "A". The ALMA data hint the episodic ejections from W42-MME. A
disk-like feature (extent ~2000 AU; mass ~1 Msun) with velocity gradients is
investigated in the source "A" (dynamical mass ~9 Msun) using the ALMA H13CO+
emission, and is perpendicular to the CO outflow. A small-scale feature (below
3000 AU) probably heated by UV radiation from the O-type star is also
investigated toward the source "A". Overall, W42-MME appears to gain mass from
its disk and the dusty envelope.
