Choose all the answers that apply. Carbon-13 has an atomic number of 6. Carbon-13 .

has two electron shells
has 7 electrons
is an isotope
is in period 2
has 7 neutrons

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

Agroup of students is studying convection current. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other is in an area with warm air. after 10 minutes, the balloon are released from a height of 1 meter. which of the following to the students most likely observe? a) the warm balloon expands and rises. the cold balloon shrinks and sinks b) the balloon both rise. the cold balloon is larger than the warm balloon c) the cold balloon expands and rises. the warm balloon shrinks and sinks d) the balloon rise at the same rate. both balloons are the same size

How much carbon is stored in the atmosphere as co2