a marriage custom in which a widower marries a sister of his deceased wife. ... a custom among the Yurok of northwestern
On a May night last year, Snitch gathered his surveillance1 team in a wild corner of South Africa. They waited until well after sunset before stealthily beginning their mission. Using a catapult2 powered by a bungee cord, the experts launched a small airplane over the deep and dark landscape, thick with acacia trees sporting 5-centimeter (2-inch) thorns.
Their robotic aircraft — or drone — is about as long as a bicycle and sports a 2.4-meter (8-foot) wingspan. In recent years, scientists have begun putting drones in the air to do many kinds of groundbreaking research. Drones carry no pilot, passengers or crew. They are often small and light. Some fly like an airplane, others like a helicopter or a blimp. Drones may fly autonomously (along a preprogrammed path) or under the control of a pilot on the ground.
That night in South Africa, Snitch and his team flew their drone by remote control over Kruger National Park. High in the sky, and under the cover of darkness, the Terrapin 1 flew undetected over the landscape. Though unseen, it could see perfectly. The experts scanned the ground using a special camera attached to their drone. This camera was designed to see anything that gives off heat, including elephants, rhinos — and people
A= 7,11
B=2,3,7
C=2,2,2,5
Because 7x11 =77 when both are prime numbers
2x3x7=42 when all 3 are prime
And 2x2x2x5=40 when all 4 numbers are prime
